Vehicle actuated traffic signal apparatus



June 12, 1956 w. H. BEAUBIEN VEHICLE ACTUATED TRAFFIC SIGNAL APPARATUSFiled Aug. 2e, 1952 5 Sheets-Sheet l Inventor: William l-l. Beauben,

His Attoney June 12, 1956 w. H. BEAUBIEN 2,750,576

VEHICLE ACTUATED TRAFFIC SIGNAL APPARATUS Filed Aug. 26. 1952 3Sheets-Sheetv 2 lnverwtorf n William HBeaubien,

by H s Ati-.ovm ey,

June l2, 1956 w. H. BEAUBlEN VEHICLE ACTUATED TRAFFIC SIGNAL APPARATUS 5Sheets-Sheet 3 Filed Aug. 26, 1952 www Inventor. William Heaubien,

His Attorrl ey.

United States Patent O VEHICLE AC'.TIJAJIEDV TRAFFIC SIGNAL APPARATUSWilliam H; Beaubien, Lynn, Mass., assigner to General Electric Company,a corporationl of New York Application August 26, 1952Serial No. 306,472

49 Claims. (ci. 34a- 35)- Myy invention relates to traiic signal controlsystems, and' more particularly to vehicle actuated tratic signalcontrol systems and apparatus therefor.

Vehicle actuated tratlic signal control systems. are distinguished. fromxed time, or pre-timed, systems'l in that avelcle actuated systeminitiates alternations of or controls the duration of the right ofwaygrantedby the traic signals tointersecting trafc lanes in direct:response. tothe presence of vehicles on. one or more of the intersectinglanes. Vehicle` actuated systems are fully actuated when subject. toactuation in response tovehicle detectors located in all of theintersecting traiic lanes,` and semiactuated when subject to actuationonly in response. to vehicle detectors located in less than all of theintersecting lanes. Fully. actuated traiiic signal control systems mayoperate so that the right of' way remains upon the trac lane to which itwas last called, known as floating operation, or the right of way mayalwaysl revert to a selected one of the traffic lanes, known asreverting operation. Alternatively, a fully actuated traiiic signalcontrol system may be operated in the absence of traftc in a normallycyclic standby manner by providing continuous automatic alternationofthe right-of way by means ot' a timer, traic actuations being operableeither to curtailor to extend the right of way intervals of the normallycyclic standby operation. it willbe appreciatedof course that asemi-actuated control system may operate normally cyclically or as areverting type, the right of way reverting to the lane in which nodetectors are provided, but is not operable as a floating system.

It will of course be understood that pre-timed traic signal controllersmustbe preadjusted to careV for one particular preselected traiiiccondition. For example, one of twof intersecting streets may be regardedas the major street and accorded more than halfthe cycle time; At some'intersections, however, the relative importance (in traii'icl density)of two intersecting streets maycliange at' different times` of the day.Vehicle actuated systems generally adapt themselves automatically tosuch changing conditions with, of course, various degrees of reinement.

It hasbeen recognizedheretofore that vehicle actuated traiiic signalcontrol systems of the fully actuated type should be provided with bothminimum and maximum right of way intervals on all intersecting lanes,and that semi-actuated traic signal control systems should .be providedWith minimum and maximum right of way intervals upon the actuated laneand with a minimum interval on the non-actuated lane. Aminimumintervalisas its name implies, the least interval accorded toanylaneonce the green light has been accorded to it. A maximum rightofway interval, as will appear, is necessary to prevent right of wayextension intervals demanded by` cars from holding a right of` waycontinuously. Without more, however, such systems becomein eiect xedtimesystems in theevent that trahie on all actuated lanesisvery heavybecause the predetermined maximum right of way inter- 2,750,576 PatentedJune 12, 1956 rice vals are repeatedly accorded to each street. Undersuch conditions', therefore, such elementaryA actuated systems fail in.their function of recognizing and operating in accordance with relativetrafc density on the intersecting lanes.

It is an object of my invention to provide a vehicle actuated traicsignal control system of the fully actuated type which may be readilyadjusted for reverting-floating or normally cyclic standby operation,and which in. all sucht modes of operation functions automatically toidetermine rightfof way intervals on intersecting traic lanes, whichintervals are continuously proportioned in accordance with the relativetratc density on the lanes, as long as traic actuations are suiiicientlyclosely spaced to preelude normally cyclic standby operation when such:operation is provided.

ltI is still another object of my invention to provide a new trafficactuated signal control apparatus wherein the limiting right of wayinterval available to any of a plurality of intersecting traiiic lanesis variable in response to relative traic density on the lanes.

A particular object of the invention is to provide, in al semi-actuatedor fully actuated traic signalcontrol apparatus, means for extending thelimiting right of way interval available on any actuated lane inresponse to vehiclesapproaching on that lane when grantedv the'right ofway.

Another object of the inventionis to provide, in'a fully actuatedtraffic signal control apparatus, rneansfor reducing the limiting rightof way interval available on any lane in response to traffic approachingon the other lane.

it i'sstill another object of my invention to provide, in asemi-actuated traic signal control system, means responsive to vehiclesapproaching on a stopped actuated traffic lane for reducingthe minimumright of wayinterval normally granted to the non-actuated lane.

A further object of'the invention is the provisionin a fully actuatedtraiic signal controller, of means for increasing the limiting right ofway interval on a moving lane in response t-o traffic approaching on themoving'lane, decreasing said interval in response to traffic approachingon the stoppedlane, and still'retaining an ultimatelimiting time whenright of way is automatically removed.

A more particular object of the invention is to provide in a vehicleactuated signalling apparatus, means for extending the limiting right ofway interval available on any traic lane in accordance with vehiclesstored on the lane between the detector and the light prior to the timesuch right of way was granted.

In a principal aspect my invention provides a` vehicle actuated timerwhich is set into operation,-normally, by the trst'car or other vehicleapproachingA the intersection against the red light. As will hereinafterappear, the timer may also be set in operation automatically, as byautomatic recall in reverting operation. Vehicles approachingona lanehaving the green light demandV and obtain vincremental extensions of theright ofy way time. To preclude permanent retention of the right of'wayby one laneY when even a single car is waiting` on the other lane, alimit, called an extension limit interval, is imposed beyond which theright of way time cannotY be extended. To-better follow trafficconditions this extensiony limiting time is variable in increments bothinv accordance with cars approaching on and cars approachproachingagainst the right of way as in a oating system. My limiting interval,however, has no arbitrarily predetermined duration but is variedincrementally, both by increase and by decrease, in accordance withexlstmg traffic conditions. Even the ultimate limiting time which isimposed despite continued efforts to increase the limit, is of no fixedpredetermined length, but is measured by the density of traicapproaching on all intersecting lanes.

In carrying out my invention in one form, I utilize a rotatable signalsequence drum which is provided with a plurality of switching positionsand which is turned from one position to another by means of an electricmotor. In its various switching positions the sequence drum actuatesswitches to control the red, amber and green lights in a traic signaldevice located at the intersection of one or more streets (hereinafterreferred to as traffic lanes). The motor driving the sequence drum iscontrolled by suitable vehicle detectors (i. e., car operated switches)positioned in or near one or more of the intersecting traic lanes, thiscontrol of the driving motor being modified, however, by a plurality oftiming devices which introduce predetermined time intervals and timeinterval limits in accordance with traffic conditions as indicated bythe repeated actuation or non-actuation of the detector switches byvehicles approaching the intersection. The detectors are normallypositioned an appreciable distance from the intersection (for example100 to 300 feet), so that vehicles crossing a detector on a lane havingthe right of way require a clearance time, and vehicles approachingagainst a red light are stored between the light and the detector.

The sequence drum is provided with certain standby or rest positions ineach of which the right of way is granted to a different one of theintersecting trac lanes, the number of stand-by or rest positions on thedrum corresponding to the number of lanes to which the right of way isgranted in a complete cycle of operation. It will be appreciated that ina semi-actuated apparatus only one such position is properly called astand-by or rest position and the intermediate right of way positions onthe drum are more properly called dwell positions. In floating orreverting operation the signal sequence drum normally remains at rest inone of its stand-by positions until it is moved to grant the right ofway to another traffic lane in response to actuations of the detector onthat other lane. In automatic recall, or normally cyclic, operation, ofcourse, the drum may also be moved Afrom the rest position or positionsin response to an automatic call circuit controlled by a manuallyoperated recall switch.

During automatic actuation under the control of the car actuateddetector switches in the intersecting street (i. e., except in stand-byoperation), the duration of the right of way granted to any actuatedtraffic lane is made up of an initial time interval determined by thecontroller in accordance with the number of cars passing over andactuating the detector switch in the stopped street prior to thetransfer of the right of way to that street, and in addition one or morevehicle extension intervals which may be added to the initial intervalin overlapping time relation in response to actuations of the detectorswitch by cars approaching the intersection on a lane having the rightof way. It is a feature of my fully actuated control apparatus that inthe event no additional car approaches and actuates the detector switchon a street after the right of way has been granted to that street, noextension time interval is granted to that street, provided of coursethat the right of way on the intersecting street is demanded byapproaching cars before the end of such initial interval.

The timers for determining the period of time that each street has theright of way, in accordance with trac conditions as evidenced byrepeated actuation or nonactuation of the car detector switches, includea timerA for each street for determining the initial time interval inaccordance with the number of cars approaching wherr the particularstreet does not have the right of way, and for adding to these initialintervals extension intervals: determined by the additional approachingcars after the street is given the right of way by the green light.

I also provide an additional timer, transferred by the sequence drumfrom one street to the other, for imposing a limiting time on the carextension intervals and moreover for transferring the right of waysubstantially instantaneously if cars are waiting on the stopped streetand cease to approach or are widely spaced on the right of way street.It is a feature of my invention as applied to full actuation that theextension limit time interval introduced by this additional timer isprogressively reduced in response to cars approaching on the stoppedstreet and progressively increased in response to cars approaching onthe right of way street. In a semi-actuated apparatus, I utilize thisadditional extension limit timer to determine a minimum right of wayinterval on the non-actuated street.

In a fully actuated controller, l provide means whereby cars approachingon a stopped lane and thus predetermining a subsequent initial right ofway interval on that lane, also increase the maximum extension intervalap plicable to such subsequent right of way interval. The extensionlimit timer, however, inherently includes anl ultimate timingcharacteristic beyond which the moving lane cannot hold the right ofway.

Itmay be further briefly noted that my controller is characterized alsoin that vehicle extension intervals demanded by cars approaching on themoving lane are not cumulative but are overlapping, each new vehicleextension interval cancelling the remaining portion of the previousextension interval, so that no more than one complete vehicle extensioninterval is stored in the timer at any one time. This characteristiccorresponds to traffic conditions, in that the vehicle interval which isoperative is that demanded by the last car to cross the detector, allother significant cars being ahead of this car.

It is a further feature of my fully actuated controller that in theevent cars cease to actuate the detector on the moving lane or arrive atintervals greater than the vehicle extension intervals, a short delay intransfer of the right of way to the other lane is imposed, so that a carapproaching on the moving lane has a time advantage or preference over acar approaching on the stopped lane.

My invention itself will be more fully understood and its variousobjects and advantages further appreciated by referring now to thefollowing detailed specification taken in conjunction with theaccompanying drawings, in which Fig. 1 is a schematic circuit diagram ofa fully actuated traic signal control system embodying my invention;Figs. 2 to 5 inclusive are simplified elementary circuit diagrams ofcertain significant timing circuits included in Fig. l, these Figs. 2 to5 being drawn for only one phase of the operation for the purpose ofsimplification; and Fig. 6 is a schematic circuit diagram of asemi-actuated trafiic signal control system embodying my invention.

Fully actuated apparatus Referring now to the drawing, and moreparticularly to Fig. 1, I have there illustrated a vehicle actuatedtrai-lic signal control apparatus suitable for application to a pair ofintersecting traic lanes. The apparatus includes a pair of vehicledetectors, or vehicle responsive switches, 1 and 2 adapted to bepositioned beneath or adjacent the intersecting traic lanes. Thedetector 1 is associated with one lane, A, and the detector 2 isassociated with the other lane, B, and each detector switch is closedmomentarily whenever a vehicle approaching on thev associated lanepasses a predetermined point spaced back `from fthe intersection. Itwill, of course,`be understood that where trac proceeds inopposite-.directions on each lane, or street, a second .detector switchwould be in parallel circuit relation with each detector switch l1 and`2. There is provided also a suitable Signal device 3of the typecomprising a red,amber and :green indicating light for each intersectingtraiiic lane. interposed 4between the detectors 1, 2 and the signaldevice 3, Tprovide a controller operable in response to actuations ofthe detectors to control the lights. This controller includes arotatable signal sequence drum 4 having switch operating cams andsixteen discrete switchingpositions, asindicated schematically inthedrawing, the drum'being advanced by a motor 5. The signal vdrum hasassociated therewith six cam operated switches, RA, AA, GA, RYB, .AB,GB, connected to control the lights in the .signal device .3. The drumalso controls a Vplurality of other -cam operated switches, C1 to C12inclusive, operable in conjunction with the various'timing circuits, aswill be 'hereinafter explained.

In addition, the controller includes five electronic timers, .each timerincluding a grid-controlled electron discharge tube, and the .tubesbeing shown as three element vacuum tubes, T-l, T-Z, T43, T-4 and T45.The timing tube T-l is in the initial interval and vehicle extensioninterval timer for the lane AA, and the timing tube T-2 is in thecorresponding timer for the lane B. yThe timing tube T-S is in theextensionlimit vand ltransfer timer, which timer is operable inconjunction with both lanes, while the tube T-4 is in an extension limitincrease timer operable in conjunction with both lanes. The tube'T-S isin an amber interval timer also operable in conjunction with both lanes.All 'the timing tubes nare arranged to be normally conductive and areprovided With grid vcapacitors which are adapted to maintain the.associated tube non-conductive when negatively charged. Each gridcapacitor is provided with one or more discharge resistors through whichany negative charge accumulated on the capacitor is permitted at timesto de- Cay, thereby to determine certain delay intervals rbefore .tubeconduction. The extension limit .and amber timing tubes T-3 and T-S,respectively, are arranged when conductive to effect Vclosure of thedrum motor energizing circuit, therebyto move the drum through asingleposition. The extension limit timing tube T-3 is vprovided withaplurality of grid capacitor discharge resistors, and these variousdischarge resistors are controlled in their connection to the timingcapacitor 'C-3 by'means of the extension limitincrease 'timing tube T-4and one or the other of the initial and vehicle extension intervaltiming tubes T41, T-2.

More specifically, the timing tubes T-1 to T-5, inclusive, are providedwith grid capacitors C-1, C-Z, C-3, C-'4 and C-5, respectively,and`witl1 anode or .plate relays R-l, `R2, R-3, R-4 and R-S,respectively. The plate relays of the timing tubes T-3 and T-S areconnected to controlthe energizing vcircuits for the program drum motorS, while the plate relays of the timing tubes T-l, T-Z and T-4 areconnected to control various discharge circuitsfor the extension limittiming capacitor C3.

The vehicle detectors 1 and 2 are connected to control :detector relaysD-l and D-2, which are connected to beheld closed'for a predeterminedfixed impulse interval upon each vehicle detection. The impulse timingof the detector relays is accomplished by a pair of detector timingrelays DT-l and DTF-2, respectively. In addition, vthere are provided anumber of transfer relays controlled 'by various contacts on thesequence drum. A transfer Arelay vTR-l is connected to control thecircuit -of the capacitor "C--1 for the timing tube T-1, and a similartransfer relay TR-Z is connected to control the circuit of .thecapacitor C-2 for the timing tube T-Z. A .pair of .transfer relays TR-Sand 'IR-4 are connected to control the cathode circuits of the extensionlimit timing tbe T-3 and to transfer the connections of these cir-.cuits in .theinoperation in .conjunction with the alternate operating.phases A Atransfer .relay "FR-5 zis ;provided to transfer @theconnections of the extension limit `increase and amber interval timingAtubes T4 and T11-5, frespectively, .in .their f different y,phases .ofoperation, and ,-a transfer .relay `'1`.R-6 is v.provided to transferconnections -of the .chargingcircuits for the timing capacitors C-i `and.C-.2 as Ythe right of way is:transferredfrom lane-to lane.

Fully actuated ope'raton-Generdl The interaction of the various timersandrelays in :controlling the ladvance of the sequence-drum 4, `andadditional functions .of the -timers and relays, will be most readily.understood by proceeding now to .describe the -operation of lthe device:under-typical y.conditions of traic actuation. ln describing theoper-ation, the .advance of the drum =wil1 be traced through onlyfavsingle .halfcycle, i. -e., from onerest position to rtheother, the otherhalf cycle being obviously effected in .an .entirely -similanman- ..ner.For the purpose `of clarity, emphasis will y'first .be placed upon themore fundamentalaspects of .the drum advance, certain improvementfeatures and rrenements being separately Adiscussedin more detail aftera single lhalfcycle of-.operation. has been traced.

Theoperation `williirst be described in conjunction Vwith Fig, .1,showingacomplete.fullyactuated apparatus. Certain Vof the-significanttubetimingcircuits-of Eig. 1 areex- .tracted `in 4elementary4diagrammatic .form at Figs. V2-5., zinclusive.

.Referring now to lFig. l, .the signal sequence drum 44 is, .asdescribed, .associated with a pluralityof vcam switches, sixof which.controlthe traicsignal device Sand there- .maining of=which `control.the various transfer :relays `and other sequencing circuits .in `thecontroller. The drum is .providedwith sixteen switching positions.representing .one complete `cycle .of operation, positions 3 :and .1-1.be- :ing the rest positions from which thedrum .w`ill.not ,ad- Vancewithout further .traflic actuation or .automatic call. .For-simplicityof illustration, .the cam switches anddrum lhave-.been-shown (LFgS. land 6') ydiagrammatically with .allswitches shown open. The horizontalbroken Alines (numbered) represent .drum positions, land the solidvertical lines -on vthe drum vindicate those drum positions in which thecam -switch vertically 7aligned `with each such -solid'lineisclosed Inposition 3 the switch .GA is fclosed, so fthat.lane.A .has the right ofway, as ndicatedon theswitch sequence diagram shown in conjunction withthe diagrammatic representation-'of the drum, while-imposition yf1.11the-switch -GB is closed, so-that lane -B has-the rightof Way..For-.the ,purpose-of illustration, .the controller `will -be considered.inth'at mode of operation in Awhich the .right vof 'way-relmains uponthe street to which it was last called. This -is the `mode of operationpreviously referred to as floatin-g operation, `and is-carried outinv.the subject controller by leaving the recall switches R1and R2 `bothopen. In ,.general, it may be'observed that'if .the sequence drumvisadvanced-from eitherposition 3 or position 11 bya vehicle actuation, thevarious -timers automatically yadvance the drum through-the intermediatepositions :to fthe -inex-.t rest position, `where the drum .then remainsuntil l.again advanced by traffic actuation, `the time 'intervals during"which Athe drum dwells'on each -of the intermediate positi ons Vbeingdetermined by various .timers i in vthe apparatus.

`Itmaynow be noted that all relays-andrelay.contacts lare shown invtlieir-deenergized positions, andsuch positionsare referred tohereinafter as dropped-.oufpositions. lt willbe understood that when any.relay is energized its contacts (shown along a single vertical '.brokenline) are all moved simultaneously to their kupper .positions, and therelay is then said to be picked-up.

iF ig. 1.-Fl0atng operation- Transfer lane .to .lane d? Let it now beassumed that the sequence drum .is in position '3, indicating AthatlaneA was 'the street to which the right of way was last called, and let itbe further assumed that no traflic actuations have taken place for aconsiderable length of time, so that the entire apparatus is in a steadystate or stand-by condition. In this condition, the lane A initialinterval and vehicle extension interval timing tube T-l and thecorresponding lane B timing tube T-Z are both conductive, since theirgrid capacitors C-1 and C-2, respectively, are discharged to the pointwhere grid-to-cathode voltage is substantially zero. The relays R-1 andR-2 are therefore picked up and the relay contacts are moved into theopposite positions from the positions shown at Fig. 1. The maximumtiming capacitor C-3, however, is charged to maximum voltage, and thetube T-3 is not conductive, both because of such charge and because itscathode circuit is open at the recall switch Rz and at a contact 43a ofthe plate relay R-2. The full charge on capacitor C-3 exists because aslow rate charging circuit is completed from a voltage divider 7 and apotentiometer 8 (as a source) through contacts 10 and 10a of relay TR-3,a cathode resistor 9, and the grid-tocathode space of the tube T-3. (Asimilar potentiometer 8a is provided for the opposite operatingcondition-i. e., drum position 11.)

In this drum position V3 also, the cam switches C1, C3, Cs, and Cs areclosed, as indicated upon the diagrammatic representation of thesequence drum. Through the cam switch C1 the transfer relay TR-1 ispicked up and its contacts 11 and 11b are positioned to connect adischarge resistor 12 across the timing capacitor C-1. Through the camswitch Ca the anodes of the timing tubes T-1 and T-Z are connected toone side L-1 of an alternating current supply transformer T, the otherside of which is represented by L-2 and the center of which is grounded.Through the cam switch Cs the transfer relay TR-S is picked up, so thatits three selector contacts 13, 14 and 15 are vproperly positioned foroperation with lane A having the right of way. Through the cam switch Csa high resistance discharge resistor 16 is connected in parallel circuitrelation with the timing capacitor C-3 of the extension limit timingtube T-3. However, the foregoing slow rate charging circuit referred toin the preceding paragraph maintains capacitor C-S charged. It will benoted that no discharge circuit is completed for the timing capacitorC-2 of the lane B timing tube T-2. In addition, the detector relays D-land D-Z and the detector timing relays DT-l and DT-Z are dropped out,while the detector switches 1 and 2 are open.

Impulse interval-1f now a vehicle actuation is received upon lane Awhich has the right of way, the detector switch 1 is closed momentarilywhile the vehicle passes over it, thereby to complete an energizingcircuit for the detector relay D-l through normally closed contacts 17,17a of the detector timing relay DT-1. (Similar contacts 18, 18a, 18hare provided on relay DT-Z for lane B detection.) When the detectorrelay D-1 picks up, it opens its normally closed contacts 19, 19a andcloses its normally open contacts 19, 19b. (A transfer contact 19C ondetector relay D-Z corresponds for lane B detection to contact 19 onD-l.) Closure ofthe contacts 19, 19bl completes an energizing circuitfrom the supply conductor L-1 through a rectilier R and a capacitor 20to the energizing coil of the detector timing relay DT-. Thus,unidirectional current is supplied to pick up and hold energized thetiming relay DT-l only for an interval suicient to charge the capacitorZtl. A resistor 20a shunting the capacitor 20 serves to determine theimpulse interval, but so limits current that the relay DT-l will nothold closed after the capacitor is charged. Energization of the relayDT-1 completes a holding circuit for the detector relay D-1 through thenormally open contacts 17, 1711 of the relay DT-l. ln this manner thedetector relay D-1 is held energized for a predetermined impulse timedetermined by the charging time of the capacitor 20, regardless of thespeed of the vehicle. When the timing relay DT-Vl drops out, the holdingcircuit for the detector relay D-1 is broken and the relay D-1 dropsout. In its drop-out, the relay D-1 again closes its normally closedcontacts 19, 19a thereby to shunt and discharge the timing capacitor 20.The relay DT-2 operates in like manner for lane B with a capacitor 21and resistor 21a.

Extension intervals.-Energization of the detector relay D-1 also opensits normally closed contacts 22, 22a, thereby to interrupt the cathodecircuit for the timing tube T-1 and render the tube non-conductive, andat the same time closes its normally open contactsy 22, 22h, thereby tocomplete a charging circuit for the grid capacitor C-1 of the tube. Thischarging circuit may be followed from the power supply line L-Z througha resistor 23, the capacitor C-1, the grid-to-cathode space in thedischarge tube T-l, the contacts 22, 22b, and the normally open contacts24, 24b on the transfer relay T-1 to the slider 25 of a potentiometer26a, 26b, 26C, 26d. Through this circuit a predetermined charge isplaced upon the capacitor C-1 which renders the grid of the timing tubeT -1 negative. Thus, when the detector relay DD-l drops out, the timingtube T-l remains n0nconductive and relay R-l is dropped out for a timesufcient to permit the negative charge upon the capacitor C-1 todischarge through the resistor 12. This nonconductive interval of thetiming tube T-1 represents a vehicle extension interval in thecontroller during which transfer of the green light away from lane Acannot be effected. Such vehicle extension interval must be suficient topermit a vehicle moving at some predetermined normal speed to clear thelight. Of course, if no car has approached on the stopped lane B, therewould be no tendency to transfer the right of way to lane B.

If, however, a car had approached on the stopped lane B at any timebeginning slightly before the approach of the car on the moving lane A(thereby to drop out relay R-Z as will be later explained), thenon-conductivity of the timing tube T-1 and consequent drop-out of itsplate relay R-l would act to prevent the transfer until the tube T-1again became conductive.

This drop-out of the lane A relay R-1 for a vehicle extension intervalinsures maintenance of the right of way on lane A because it preventsrapid discharge of the extension limit timing capacitor C-3. Referringto the grid circuit of the extension limit timing tube T-3, it will beobserved that three discharge resistors 16, 27 and 28 are provided. Thecapacitor C-S cannot discharge through the resistor 27 even though anormally open contact 29 on the detector relay D-l is momentarily pickedup, because the detector relay D-2 is dropped out (to open its contact30) and contacts 31, 31b on the transfer relay TR-3 are open. Thecapacitor C-3 is not discharging through the resistor 16 because thecharge on C-3 is being maintained through resistor 9 as previouslydescribed. The resistor 28 is a relatively small transfer resistorthrough which the capacitor C-.3, when connected, may dischargeinapproximately one second. This resistor 23, by thus rapidly dischargingthe capacitor C-3, effects a substantially immediate transfer of theright of way by rendering the timing tube T-S conductive, as will bepointed out hereinafter. However, because of the drop-ont of the platerelay R-l for lane A, the capacitor C-3 cannot discharge throughresistor 28 at least until the relay R-l (which is measuring a vehicleextension interval) is again picked up. This is because the dischargecircuit for capacitor C-3 through the resistor 28 must be followed fromthe grid of the tube T-3, through the drum contact Cs, normally opencontacts 32, 32h on the plate relay R-4 (now closed because the tube T-4is conducting), a normally open contact 33 on the lane A transfer relayTR-l (now closed through drum contact C1), and normally open contacts34, 34b on the lane A plate relay R-l. The contacts 34, 34h, now beingheld open for the duration of a vehicle extension interval, on thetransfer resistor 28 cannot be con- 'andere nected across 'the capacitorlC-'3 even if a car does approach on the stopped lane B (which dropsoutplate relay 'R2 thereby to close the cathode circuit of tube T-3 aswill appear hereinafter).

Initial interval measurement- If now a car approaches on the stoppedlane B (i. e., against a red light) during the vehicle extensioninterval previously described, the detector relay D-2 is momentarilypicked up. This momentary pick-up is through detector 2 and contacts 18,18a of relay DT-Z, and is timed by capacitor 21, in the same mannerpreviously describedfor a lane A actuation. When relay D-2 picks up, itopens the cathode circuit of the timing tube T-2 at its contacts 35, 35aand completes a charging circuit for the lane B timing capacitor C-2 4byclosure of its contacts 35, 35b. This charging circuit may be followedfrom a point 36 on a potentiometer 37a, 37b, 37e, 37d, through contacts38, 38a on relay r1R--6, the capacitor C-2, the grid-to-cathode space in'the discharge tube T-2, the contacts 35, 35b on the detector relay D-2,normally closed contacts 39, 39a on the transfer relay TR-Z, and avariable resistor 40. A similar resistor 40a is provided in the likecharging circuit of capacitor C-1. This charging circuit is closed onlymomentarily by the detector relay D-2 so that a small predeterminedimpulse or increment of charge is placed upon the capacitor C-2, therebyto render the grid of the discharge tube T-2 negative. Additional lane Bdetector actuations by cars approaching the red light add furtherincrements of charge to the capacitor C-2, thereby predetermining alonger discharge time for the capacitor when a discharge circuit islater completed through its associated discharge resistor 41. As willhereinafter appear, this incremental charging of the capacitor C-2 bycars approaching on the stopped lane predetermines an initial right ofway interval for lane B when the right of way is transferred tothatlane.

Also, the charging of this capacitor C-2 by the approach of the rstvehicle on the stopped lane B renders the tube T-2 non-conductive,thereby to drop out the lane B plate relay R2. When the relay R-2 dropsout, it closes its normally closed contacts 42, 42a and 43, 43a. Thesecontacts 42, 42a prepare a discharge circuit for the eX- tension limitcapacitor C-3 through the rapid transfer resistor 28. This dischargecircuit, however, remains incomplete so long as cars approaching themoving lane A are retaining the relay R-l dropped out 'to time vehicleextension intervals, thus maintaining the contacts 34, l34b open.

The contacts 43, 43a complete connection of the cathode of tube T-3 tothe supply line L-2. This connection shunts resistor 9 and potentiometer8 and thus initiates discharge of capacitor C-3 through the extensionlimit resistor 16, thereby to begin the timing of an extension limitinterval for the moving lane A.

Transfer.-With cars thus waiting on the stopped 'lane B as described, itmay now be observed that if a sufficiently long break in the trafficapproaching on the moving lane A occurs so that the vehicle .extensioninterval demanded by the last preceding car expires without another carapproaching, the timing tube T-1 again becomes conductive thereby'toenergize its plate relay R-1 and close the contacts 34, 34h. Thisprepares a discharge circuit for the capacitor C-'3 through the rapidtransfer resistor 28, the contacts 42, 42a on relay R-2, the contacts34, 341; on relay YR-l, the contact 33 on relay'TR-l, the contacts '32,3'2b on relay R-4, and the drum contact Ca.v

It may now be noted that the foregoing discharge circuit for the rapidtransfer resistor 28 is delayed in completion when, as described,vehicle extensions have been demanded by cars on thegreen lane A.Whenever alane A extension interval expires so that the plate relay R-1picks up, as described, this relay not only recloses contacts 34, 34h,but also closes its contacts 44, 4411 toplace a pair of resistors 45 and46 in parallel in .the charging circuit of capacitor C-4. VThe resultingchange in grid voltage ontube T-4 causes thattube Vto shut off and relayR-4 to drop out for a short delayinterval whenever the relay R-`1 picksup. The discharge vcircuit -for. 4C-S through resistor 28 is completedwhen T-4againconducts. This delay insures full discharge of capacitorC-l to la predetermined voltage prior to transferfof theright'of way tolane B so that'the initial interval charging'increments thereaftereffective on capacitor C-l start at a 'predetermined capacitor voltage.

The foregoing delay in discharge of C-'3 by shut-otfof tube T-4 is notpresent when the now moving laneca'rs have been holding the right of wayagainst waiting cars on the stopped lane (i. e., when relay R-lvdroppedout before relay R-2 dropped out to close contacts 43, 43a).

It may now be noted that vehicle extension intervals demanded by carsapproaching in the moving lane -A do not accumulate, but each extensionvinterval cancels the remaining portion of the preceding interval vandre-starts the timing of a `single extension interval. Thisisbecause ofthe fact that upon each actuation kthe lane A timing capacitor C-l isalways charged up to a Ypredetermined maximum voltage determined by thesetting of 'potentiometer'26a, 26h, 26e, 26d.

Referring now again to the transfer operation effected by discharge ofthe capacitor C-3 through the resistor 28, it may be noted that theresistor 28 is preferably "of relatively low resistance so that thecapacitor C3 discharges throughthis resistor in about one second. Uponsuchfdischarge, the extension limit timing tube T-'3 is krenderedconductive so that the associatedplate relay R-3 is picked up and closesits 'normally open contact 47, thereby to complete an energizing circuitfor the drum advance motor S from the power supply line L-2 to ground.

It will now be evident Athat if cars approaching on *the initiallymoving lane A had continued `to demand Vehicle extension intervals, i.-e., no suicient break in 'lane yA traic to permit expiration of anextension interval, the contacts 34, 34b of the lane Afplate relay R-lwould have remained open Vso that the capacitor C-3 could not vdischargethrough the rapid transfer resistor 23. Eventually, however, thecapacitor C-3 would have vbecome discharged through the extension limitresistor 16 which is connected across this capacitor by the drumcontact'Cs. Thus, veither `because ofexpiration of the extension limittime or because of a breakin lane Amoving traiic, the extension limittiming `tube T-3 is rendered conductive as described, 'therebyto pick upits plate relay and energize the motor "5 to advance the drum.

It may be here noted that when transfer of the Yright of'wayis effectedbythe presencevof lane B waiting cars beforethe lane A limiting time hasexpired and by reason of 'a break in lane A trai-lic, the transfer is'effected -by rapid discharge of C-3 through resistor l28. Thisdischarge takes a short time, for example, one second, so that if duringthis discharge a car actuates the detector on the green lane A, such cartakes preference over the cars waiting on lane B in that the lane Aplate -relay R-i .is again dropped out 'for one extension interval toylinterrupt at contacts 34, 34b discharge of capacitorfC-S throughresistor 28. lSuch preference, however, is not gi-venwh'en transfer iseiected by discharge of C-3 through 'there-X- tension limit resistor'because'this discharge isfno't affectedby cars on the 'streethavingftheright of way.

VAdvance of thedrum 4 toward position 4imrnediately closes thedrumcontact'Cv, thereby to pick up the vtransfer relay TR-4 and open'the cathode circuit forthetiming tube T-3. Thisrenders -the tube T-3nonconductive so :that the plate relayR-S is droppedout `andthernotor5,.deenergized. By reason of a capacitor 48 .connectedin series with arec'tier 49 across the lmotor 5, and a resistor 50 shunting the rectier49, a charge stored inthe .capacitor 48 discharges through the motor,thereby to .brake the motor .to a stop atposition 4 of thetdrum. Thismotor braking circuitlismorefully describedandfclaimedinmy copendingpatent application, Serial No. 271,799, tiled February 15, 1952, forElectric Motor Braking Systems. When the drum arrives at position 4, itcompletes another motor energizing circuit operative to drive the drumto position 5, as will be later described, so that the drum only pausesbriefly in position 4.

Pick-up of relay 'TR-4 in drum position 4 also completes a chargingcircuit for the extension limit timing capacitor C-3. This chargingcircuit may be followed from the potentiometer Sa (or 8 in the oppositeright of way condition at drum position 12), through the relay contacts10, b, contacts 51, Slb on relay 'fR-4, the grid-to-cathode space oftube T-3, the capacitor C-3, and the voltage divider 7.

It will be observed from the drum diagram that in this position 4 of thedrum the green light on lane A is deenergized and the amber lightsubstituted therefor. T he red light still remains on lane B. It will befurther observed that through -drum contact C1 the A transfer relay TR-lis dropped out, thereby to remove the resistor 12 from its shunt circuitrelation with the capacitor C-l and prepare the capacitor C-l for theaccumulation of an initial interval charge as heretofore described inconnection with capacitor C-2. The drum contact C7 is closed in position4 as heretofore described. Furthermore, the drum contact C9 is closed inposition 4, thereby to energize the transfer relay TR-3. When thetransfer relay TR-3 picks up, it transfers its selector contact 10 from10a to 10b thereby to transfer the charging circuit for the extensionlimit timing capacitor C-3 from a lane A potentiometer 8 to a lane Bpotentiometer 8a. The transfer relay "fR-3 also transfers its contact 31thereby to close the contacts 31,`31b and open the contacts 31, 31a,thus associating the discharge resistor 27 with lane A rather than withlane B. The purpose and operation of resistor 27 will be describedhereinafter. Transfer relay TR-S also transfers a contact 52 from 52a to52h thereby to transfer control of the cathode circuit of the timingtube T-3 to the lane A rather than the lane B plate relay. Finally, therelay TR-3 transfers a pair of contacts 53 and 54 to transfer certaincapacitor charging circuits from lane A to lane B operation, as willhereinafter become more evident, and transfers a contact 5S. Thiscontact 55, as Well as contacts 56 and 57 (now transferred by relayTR-4), introduces a memory feature into the operation as will behereinafter more fully described.

Finally, advance of the drum to position 4 closes the drum contact C12,thereby to complete an energizing circuit from the power supply line L-2to the motor 5 and advance the drum from position 4 to position 5.

In position 5, no change is effected in the lighting circuits nor in theother drum contact positions so that the motor 5 remains energizedthrough the drum contact C12 and thus advances the drum to position 6.This position is thus a dummy position provided to facilitate the use ofa standard sixteen-position drum.

In position 6, the motor 5 is deenergized at the contact C12 and brakesto a stop through the circuit 48, 49 and 50. In this position 6, thereis still no change in the lighting circuits, but it will be noted thatdrum contacts C4 and C5 are now closed and drum contact C7 opened. Thedrum contact C4 energizes the transfer relay TR-6, and the drum contactC7 drops out relay TR-4, which opens its contact 51, 5117 to interruptthe charging circuit of capacitor C-3 and prepare the tube 'I`-3 forconduction. The drum contact C5 completes the cathode circuit of theamber timing tube T-S.

Amber timing-Referring first to the amber timing circuit, it will beobserved that the cathode circuit for the amber timing tube T-5 iscompleted only in drum positions 6, 7, 8 and 14, 15, 16. The tube T-S istherefore non-conductive in all other drum positions. At Fig. 2, I haveshown a simplified circuit diagram of the amber timer circuit alone,using the same reference numerals as at Fig. 1 and showing principallythe components involved in transfer of the right of way from lane A tolane B.

It will rst be noted that prior to closure of the contact C5 a chargingcircuit is complete for the capacitor C-S of the discharge tube T-5,which circuit may be followed from the power supply line L-2, through avoltage divider 58, the capacitor C-S, the grid-to-cathode space of thedischarge tube T-S, a resistor 59, the contacts 15, 15b of the transferrelay TR-S, and a potentiometer 60. (A similar potentiometer 61 isconnected by contacts 15, 15a if lane B amber is being timed.) Thepotentiometers 6l) and 61 and the voltage divider 58 are so set thatwhen the line L-1 is positive, the tap 58a on the voltage divider 5S isnegative with respect to the slider 60a on the potentiometer 60 (or theslider 61a on the potentiometer 61). When the power supply line L-1 isnegative, the point 58a is positive with respect to the slider 61M (or61a) and grid current flows through the discharge device T-S to chargethe capacitor C S to the difference Voltage between the points 58a and60a (or 61a). The capacitor C-S thus stands charged at the time that thedrum moves into position 6. Thus, when the drum contact C5 closes, thepotentiometer 60 is shunted by resistor 59. The negative charge on thecapacitor C-S now leaks olf through resistor 62 and is reduced to thepotential difference between that of the power supply line L-2 and thepoint 58a on the voltage divider 58. During the decay of the charge oncapacity C-S, the amber timing tube T-5 is retained nonconductive. Whenthe capacitor C-S is discharged sufficiently so that the amber timingtube T-S becomes conductive, the associated plate relay R-S is pickedup, thereby to close a normally open contact 63 and cornplete anenergizing circuit for the duim advance motor 5. When the amber timingplate relay R-S is picked up, it also closes another normally opencontact 64 which completes a minimum interval charging circuit forcapacitor C-2 (or C-1 as the case may be) as will be more fullydescribed hereinafter. Thus, the drum is advanced from position 6 toposition 7.

Referring back now to the closure of the drum contact C4 when the drumarrived at position 6, it will be noted that this drum contact energizedthe transfer relay TR-6. When this relay is energized, it transfersseveral. selector contacts 65, 33 and 66. Transfer of the contact 65removes line L2 power from two detector timing relay contacts 67 and 68and places L-2 power upon contacts 34 and 42 of the lane A and lane Bplate relays, respectively. Transfer of the contact 38 removesconnections of the line L-2 from the point 36 on the potentiometer37a-37d and connects this line directly to contact 54h on the transferrelay TR-3, and thus through the contact 54 on 'fR-3 (now picked up) andthe amber plate relay contact 64 (closed after the amber timinginterval) on the contact 53 of the transfer relay TR-3, thereby toprepare for minimum initial interval timing for lane B as will be morefully described hereinafter.

The drum now having advanced to position 7, it will be noted that stillno change is effected in the lighting circuits, and that no change iseffected in any other of the drum contact circuits except the drumcontact C12, which is now again closed. Closure of the contact C12insures energization of the drum advance motor 5 so that the drumadvances to position 8.

At drum position 8, the lighting circuits are still unaffected, but thedrum contact Cs is closed. Closure of the drum contact Ca again connectsthe maximum extension limit timing resistor 16 across the extensionlimit timing capacitor C-3, thereby to prepare for the timing of anotherextension limit interval. In position S, the drum contact C12 is stillclosed so that the drum advance motor 5 is still energized and the drumadvances to position 9.

In position 9, the drum contact C5 is opened so that lthe cathodecircuit of the amber discharge tube T-S is interrupted, thereby tointerrupt conduction of this timing tube, whereupon its plate relay R-Sdrops out, thereby to open the contact 63 and 64. In drum position 9also, the green light for lane B is energized through the drum contactGB, the red light for lane B is deenergized at the drum contact RB, theamber light for lane A is deenergized at the contact AA, and the redlight for lane A is energized through the Contact RA. In this position 9of the drum, the drum advance contact C12 is also opened and the drumcontact C11 closed. Closure of the contact C11 short circuits theportion 37b, 37C of the potentiometer 37a--37a- Difference interval-Whenthe potentiometer 37a- 37d is thus partially short circuited, provisionis thereby made for setting up the capacitor C-2 (which has thus faraccumulated increments of initial interval charge) to time a differenceinterval. This difference interval is constituted approximately of theaccumulated initial interval less one vehicle extension interval, andhas for its purpose to eiectively increase the lane B extension limittime in accordance with cars stored on the now green lane B between thelight and the detector (these cars having arrived on lane B VWhile red)in the same manner as if they had arrived on line B while green. This isnecessary because cars stored on lane B (now green) behind the detectordo not have an opportunity to increase the extension limit by crossingthe lane B detector (as further described hereinafter) until the carsahead of the detector are cleared.

The foregoing difference interval is prepared in position 9 in thefollowing manner. In this position, relay TR-2 is picked up, ashereinafter pointed out, and relay TR-6 is also picked up as previouslypointed out. By this action, contacts 38, 38a of relay TR- and contacts69, 69a of relay rl`R-2 disconnect the capacitor C-2 from the normalcharging voltage point 36 on potentiometer 37a-37d. Also, closure ofcontacts 69, 69h of relay rl`R-2 shunts the portion of potentiometer37a-37d through a small capacitor 70 and a resistor 71 in series andconnects capacitor C-2 to the common point of capacitor 70 and resistor71. (A capacitor 7a and resistor 23 are similarly connected topotentiometer 26a- 26d in transfer of right of way from lane B to laneA.) At the same time, drum contact Cn is closed so that thecharging-potential on capacitor C-2 is now determined in effect by theslider 72 on potentiometer 37a-37d. Now therefore, if the slider 72 ishigher in potential than the accumulated voltage on capacitor C-2, thentube T-2 conducts immediately in drum position 9. Iny this case, thedifference interval is not effective. If, however, the potential ofslider 72 is less than the. accumulated negative voltage of capacitorC-2 (i. e., many cars are stored on lane B), then tube T-2 is maintainednon-conductive only until the stored capacitor voltage decreases byleakage to equal the potential of Slider 72. This represents thedifference interval. During this difference interval, the cathodecircuit of tube T-4 is interrupted at contacts 65, 65a of relay TR-G,thereby to extend the extension limit time, as will be later pointedout.

In this drum position 9 also, the drum contact C10 is closed, thereby tocomplete an energizing circuit for the lane B transfer relay TR-Z. Whenthe transferv relay TR-Z picked up, it closed its normally open contacts69, 69h thereby to connect the discharge resistor 41 across the lane Btiming capacitor Ce2. It will be recalled that the timing capacitor C-Zwas previously charged in increments by cars approaching on lane B whenthat lane had the red light, such accumulated charge representing theinitial interval. This capacitor, therefore, is retaining the grid ofthe tube T-Z negative and that tube non-conductive. When the resistor 41is connected across the capacitor C-Z by energization of the transferrelay TR-Z, the capacitor C-2 begins to discharge. As described 14above, this discharge takes place only down to the point where thevoltage of C-2 equals that of potentiometer slider 72 (i. e., if slider72 is at the initially higher voltage). That is, the timing tube T-2 ismaintained nonconductive for a difference interval determined by theextent of the charge previously accumulated on the capacitor C-2 and thevoltage of slider 72. When tube T-2 conducts, relay R-Z picks up,thereby to lenergize the drum motor 5 through a circuit which may befollowed from the motor through contacts 32, 32a of relay R-4, a contact73 of relay TR-Z, contacts 42, 42b of relay R-2, and -contacts 65, 65bof relay TR- to L-2 power. The drum 4 therefore advances to position 10.

Initial interval timing-In drum position 10, no change is effected inthe lighting circuits. The drum contact C4 is opened. The drum contactC11 is also opened, and the drum contact C3 is opened. Opening of thedrum contact C3 disconnects the plates of the lane A and lane B timingtubes T-1 and T-2 from the power supply line L-1 so that these tubescannot become conductive in drum position 10. This drum position 10,however, is only a transfer position, for in this position the drumcontact C12 is momentarily closed, thereby again to complete anenergizing circuit for the drum advance motor 5 and move the drum toposition 11. In position 11, the energizing circuit for the motor 5 isinterrupted by re-opening of the drum contact C12 and the plate circuitsof the discharge tubes T-1 and T-2 are reconnected to this power supplyline L-1 by -reclosure of the drum contact C3. l

In this drum position 11, the tube T-Z is now maintained non-conductivebecause of the negative charge still remaining on the capacitor C-2 (i.e., not dissipated during the difference interval and representing theremainder of the initial interval for lane B). So long as the dischargedevice T-2 is non-conductive, no transfer of the right of way to lane Acan be initiated because of the dropped-out position of the associatedplate relay R-2. The reason for this is similar to the descriptionhereinbefore of the manner in which drop-out of the lane A plate relayR-1 for vehicle extension intervals precluded transfer of the right ofway to lane B for such extension intervals.' Briefly, it will berecalled that so long as the plate relay R-l or R-Z of that lane havingthe green light is dropped out, dis-charge of the extension limit timingcapacitor C-3 through the rapid discharge capacitor 28 is precluded. Inthis drum position 11, therefore, the relay R-2 picks up at thetermination of the remainder of the initial interval (or at thetermination of such interval plus one or more vehicle extensionintervals if they are demanded by cars approaching on lane B). The tubesT-1 and T'-2 are now in their normal conductive conditions for lane Bright of way, just as for lane A right of way in drum position 3.

Rest.-It will now be recalled, and may be further observed by inspectionof the drawing, that position 11 on the drum is a normal or restposition in which the right of way is granted to lane B, in the samemanner as position 3 is a rest position in which right of way is grantedto lane A. It will thus be evident that with the drum in position 11 theright of way is on lane B so that the timing capacitor C-2 may berecurrently charged as a result of actuations of the lane B detector 2,thus pre- -cluding transfer of the right of way for predeterminedvehicle extension intervals; while vehicles approaching the intersectionon the now stopped lane A effect incremental charging of the timingcapacitor C-1, thereby to store an initial charge in this capacitor fordischarge to determine an initial vehicle interval when the right of wayis restored to lane A.

It will be further evident that return of the right of way from lane Bto lane Av by transfer of the drum from position 11 to position 3 takesplace in a manner similar tothat described above, for transfer of thedrum from position 3 to position 11, so that no further description ofthis action is deemed necessary. Those skilled in the art will nowappreciate that certain circuit components identified by referencenumerals on the drawing but not specically referred to in the operationare useful only in this second half cycle, and their correspondence offunction to components already described will be readily discerned fromthe drawing and description.

The initial and extension interval timing circuit for tube T-l and drumposition 3 is shown in simplified form at Fig. 5, using the samereference numerals as at Fig. l. The operationwill be fully understoodfrom the foregoing description of Fig. 1.

In view of the foregoing description of the operation, certain otherfeatures of loperation not previously mentioned may now be more readilyfollowed.

Extension limit time decrease It may first be noted that the extensionlimit time determined by discharge of the capacitor C-3 through thelarge extension limit resistor 16 is not a fixed time, but is subject toreduction in response to the approach of vehicles on the stopped lane.This is done by momentarily connecting the discharge resistor 27 inparallel circuit relation with the resistor 16 each time that a vehicleapproaches the intersection on the stopped lane, thereby more rapidly todischarge C3 in recurring increments. It may be observed that suchparallel connection is effected either through the contact 29 of thelane A detector relay D-l, or the contact 30 of the lane B detectorrelay D-Z, one or the other of these contacts being selected by thecontact 31 on the transfer relay 'TR-3. For example, in position 1lwhere lane A is stopped, the relay TR-3 is energized through the drumcontact C9 so that the contact 3l is closed on the contact 31h. The laneB detector relay contact 30 is therefore disconnected from the circuitand the stopped lane A detector relay contact 29 is connected incircuit, thereby to connect the discharge resistor 27 in parallelcircuit relation with the resistor 16 momentarily each time that thedetector relay D-1 is picked up for a predetermined impulse interval bythe detector 1 on lane A. In this manner, the extension limit intervalfor which the green light may be held by cars approaching theintersection on the moving lane is progressively reduced as more andmore cars accumulate between the intersection and the detector on thestopped lane.

Extension limit time increase In addition to the foregoing, theextension limit time determined by the discharge of capacitor C-3through resistors 16 and 27 is subject to increase in response to carsapproaching the intersection on the moving lane by the operation of theextension limit increase timing tube T-4 in the following manner. Theextension limit increase circuit of Fig. l is shown in simplified format Fig. 3, using the same reference numerals as at Fig. l and showingonly components used with lane A green.

Not previously mentioned was the fact that the timing tube T-4 isnormally Vconductive so that its plate relay R-4 is normally picked up,thereby normally to connect a discharge resistor 74 in parallel circuitrelation with the extension limit resistor 16. The cathode circuit forthe timing tube T4 may be followed from the cathode through the selectorcontact 13 on the transfer relay TR-S and then through one or the otherof the detector timing relay contacts 67, 68, to the power supplyconductor L-Z through the transfer contact 65 on the transfer relayTR-6. Thus, except when the relay TR-6 is picked up in positions 6, 7, 8and 14, 15, 16, the discharge tube T-4 is conductive. It will be notedalso that the discharge tube T-4 is provided with a grid capacitor Cedacross which is shunted a discharge resistor 7S, one end of thecapacitor C-4 being connected to an intermediate point 76 on apotentiometer 77a, 77h, 46. Thus, if either of the detector timingrelays DT-l or DT-Z is picked up, the contact 67 or 68 connects thecathode of the discharge device T-4 to the sliderv 77 on thepotentiometer 77a, 77h, 46 on the opposite side of ground from the point76.

It will now be evident that in operation the extension limit increasetiming tube T-4 is normally conducting. Upon actuation of the detectorin the moving lane, for example, in drum position 11 on lane B, thedetector relay D-2 is picked up and the detector timing relay DT-il ispicked up. When the relay DT-Z is picked up, the cathode circuit of thetube T-4 is interrupted at the contact 68 and the same contact connectsthe cathode of the tube T-4 to the point 77 on the potentiometer 77a,'77b, 46. This causes the capacitor C-4 to be charged on half cycleswhen the line conductor L-2 is positive, thereby to render the grid ofthe discharge tube T-4 negative. Thus, when the detector relay D-Z andthe detector timing relay DT-Z again drop out after a predeterminedimpulse interval, the tube T4 is retained non-conductive sufficientlylong for the predetermined charge to leak off the capacitor C-4. Duringthis short timing interval, the plate relay R-4 is dropped out, therebyto discon neet the discharge resistor 74 from its normal parallelcircuit relation with the extension limit resistor 16. In this manner,the rate of discharge of the extension limit capacitor C-3 istemporarily reduced, thus increasing the extension limit interval inresponse to detector actuations on the moving lane.

Ultimate extension limit time It will now be evident that even thoughcars approaching on the stopped lane are able progressively to decreasethe extension limit time by connecting the resistor 27 in parallelcircuit relation with the resistor 16, and cars on the moving or greenlane are able progressively to increase the extension limit time bydisconnecting the resistor 74 from its normal parallel circuit relationwith the resistor 16, the resistor 16 itself being connected across thecapacitor C-3 only by the drum contact Ca, insures that an ultimatelimiting time is always imposed for discharge of the capacitor C-3 oncethe timer has been started in operation. Stated in another way, theextension limit interval increase and decrease resistors 74 and 27,respectively, merely decrease or increase the rate of discharge of thecapacitor C-3, but do not in any event recharge the capacitor. Thus, theextension limit interval timer (including tube T-3) always possesses anultimate time limit characteristic, despite the fact that the limitingtime may be increased by cars approaching the green light.

This ultimate discharge time is, of course, not of fixed predeterminedduration, but depends upon trac conditions. The ultimate limit is, ofcourse, simply a mode of operation of the extension limit timer, so thatfor any particular tratiic condition the limit time is fixed. In theextreme case, if no cars approach onrthe street having the red light,and if cars approach continuously on the street having the green light,continuous effort is made to increase the extension limit time byremoving resistor 74 from the discharge circuit of capacitor C-3. Eventhough resistor 74 is, continuously held Vdisconnected, and resistor 27never connected in circuit, the capacitor C-3 will ultimately dischargethrough capacitor 16 and will impose an ultimaterlirniting time. Underthe one extreme condition assumed, of course, this ultimate time ispredetermined.

Fig. 4 shows a simplified circuitdiagram of the extension of transfertimerT- for one half rcycle of operation, using the same referencenumerals as at Fig. 1.

Minimum initial interval timing Attention is now directed to a featureof initial interval charging not heretofore mentioned. ,It will berecalled that the initial green interval onY any lane has been describedas being timed by recurrent incremental chargafferisce ing of the timingcapacitor (C-1 or C-2) associated with that lane by cars approaching onthat lane when it has the red light. This is done by recurrently pickingup the stopped (i. e., red) lane detector relay (D-l or D-Z) for apredetermined impulse interval upon each vehicle actuation on thestopped Such pick-up momentarily completes a charging circuit which maybe followed, for capacitor C-Z for example, from the resistor 40 throughcontacts 3d, 39a on relay TR-2, contacts 35, 35h on relay D-Z, thegrid-tocathode space of tube T-Z, the capacitor C-2 and a resistor 7S toline L-Z. (A similar resistor Ida is provided for the lane A timing tubeT-1.)

ln the event such charging increments do not add up to a charge ofpredetermined minimum voltage, representing a predetermined minimuminitial interval, means are provided to bring the charge always to suchminimum value. This is done for the respective phases by means ofvariable potentiometers 79 and d0, the operable po tentiometer for eachlane operation being selected by the contact 53 on relay TR-3. Acharging circuit for initial interval charging is completed during rightof way transfer operation. For example, for transfer from lane A greento lane B green, transfer relay TR-6 is picked up in drum positions 6 9,inclusive, to complete a charging circuit for capacitor C2 which may befollowed from the slider 79a of potentiometer 79 through contacts 53,53h of relay 'fR-3, contact 64 of amber plate relay R-S (which picks upin drum position 6 after timing the amber display), contacts 54, 54b ofrelay 'FR-3, contacts 38, 38]) of relay "fR-6, capacitor (2 2, thegrid-tG-cathode space of tube T-Z, and contacts 35, 33a of relay D-1 toline L-Z. The like operation for reverse transfer of the right of waywill be evident to those skilled in the art.

Memory feature Attention is now directed to the memory function ofcontacts '5, 56 and 57 on relays 'TR-3 and TR-d. If the right of way istransferred from lane A by reason of expiration of the extension limittime before the end of a vehicle extension interval then running on laneA, then when the drum is passing through positions 4 and 5, detectorrelay D-l is picked up through contacts 44, 44a of relay R-l, contactsS2, 52h of relay TR-3, contacts S6, 56h of relay 'fR-1i, contacts 55,5512 of relay 'TR-3, and contacts 17, 17a of relay D'lll, Pick-up ot'relay D-l stores a single increment of charge on capacitor C-1 in thesame manner as if a car had approached on lane A against the red light.This extends the time for which right of way is restored to lane A byreason of the call already requested by the existing deenergization ofrelay R-l under such conditions. The same action takes place if acontact 31 on relay R-d is closed by reason of short interval drop-outof R-d whenever relay R-1. picks up. Thus, the short drop-out intervalol R- after R-l picks up (i. e., lane A extension expired) is includedin the period during which memory may be registered.

Automatic recall lt will now be readily possible to appreciate thefunction and operation of the recall switches R1 and R2. In theforegoing description, it has been assumed that both recall switcheswere open. In this condition, the apparatus operates to retain the rightof way on the street last called (i. e., floating). rfhis is because,when the recall switches are open, the cathode circuit of tube T-3 (thetube conduction of which initiates transfer) is not completed (throughcontacts d3, 43u of relay R-Z) until a red street actuation takes place.

However, with the recall switch Rt, for example, closed, the contactslid, da of relay R1 are shunted so that switch R1 registers an automaticrecall of right of way to lane A in the same manner as the memoryoperation described above. Switch R1 also completes the cathode circuitof tube T-3 so that T-3 will conduct to initiate a re-transfer of rightof way to lane A as soon as all eX- 1S tension time on lane B hasexpired (i. e., C-3 is discharged) despite the fact that no actuationhas occurred on lane A to drop out relay R-l.

Similarly, an automatic recall is placed in drum position 3 by closureof switch R2. l'f both switches Rt and R2 are closed, cyclic standbyoperation results, and it will be evident that if no cars approach oneither street with both R1 and R2 closed, the cyclic right of way timeon each street is the minimum initial interval time previouslydescribed.

Semi-actuated apparatus At Fig. 6, I have illustrated certain featuresof my invention as embodied in a semi-actuated traflic signal controlapparatus. The apparatus illustrated at Fig. 6 is applicable to theintersection of a pair of traffic lanes, and it will be understood fromthe foregoing that only the minor lane B is provided with a detector.

The apparatus illustrated at Fig. 6 bears a general resemblance to thatillustrated at Fig. l in that there is provided a vehicle detector 101adapted to be positioned beneath or adjacent the roadway on the minortraiiic lane B, a signal indicating device 102, a rotatable signalsequence drum 103, and a plurality of electronic timing tubes T-ll,T-3l, T-lll and T-Sli for controlling the advance of the drum to varythe display of signal lamps in response to actuations of the detector.The signal sequence drum 193 is connected to be advanced in steps by amotor 16d having a braking circuit 105' similar to that shown at #i3-S0ol' Fig. l. As at Fig. 1 also, the signal sequence drum 1113 is providedwith six signal lamp switches RA, AA, GA, RB, AB, and GB. In addition,the drum is provided with a plurality of other cam switches C2i, C22,C23, C24, C25, C26 and C27 which are operable in conjunction with thevarious timing circuits in a manner which will hereinafter be explained.

The controller of Fig. 6 includes four electronic timers each includinga grid controlled electron discharge tube, such as the three-elementvacuum tubes 1111, Te31, T-41 and T-Sl. The timing tube T-ll is arrangedto time the initial interval and vehicle extension intervals for theminor lane B. The timing tube T-31 is in an extension limit and transfertimer and corresponds in a general way to the timing tube T-3 of Fig. 1.The extension limit timing function of the tube T-31 is applicable onlyto the minor lane B in the case of Fig. 6. The timing tube T-41 is in anextension limit increase timer and corresponds in a general way to thetiming tube T-4 of Fig. l; and the timing tube T-'Sl is in an ambertimer for both streets and corresponds to the timing tube T-S of Fig. l.In addition, the timing tube T-31 opcrates to time a xed initial orminimum interval for the major lane A. As will hereinafter appear, meansare provided in the apparatus of Fig. 6 for incrementally reducing thislane A minimum time in response to actuations of the Vdetector 101 onlane B when that lane is stopped.

As in the apparatus at Fig. l, each of the timers including the tubesT41, T41, T-41 and T-51 includes also a grid capacitor which whencharged maintains the tube nonaconductive, and one or more dischargeresistors adapted to be connected across the capacitors. Specically, thetube T-ll is provided with a grid timing capacitor C-11, the tube T31 isprovided with a grid capacitor C-31, tube T-ll is provided with a gridcapacitor C-41 and the tube T-S1 is provided with a grid capacitor C-51.In addition, the timing tubes are provided with anode or plate relaysiii-11, R-31, R-41, and R-Sl, respectively. The detector lill isconnected to control a detector timing relay DT-ll, and the relay DTllis connected to control a detector relay D-ll. Impulse timing of therelay DT-11 is accomplished by a simple series capacitor 107. Inaddition, there are provided three transfer relays r.FR-11, TR-Zll andTR-31 controlled 'respectively by the drum contact C22, C25,

and RB. Power is supplied to the timers, relays, lights and drum motorfrom a transformer T-1 through power supply lines L-1 and L-2, thecenter of the transformer secondary winding being grounded.

Semi-actuated operation-General The interaction of the various timersand relays in controlling the advance of the sequence drum 103, andadditional functions of the timers and relays will be more readilyunderstood by proceeding now to describe the operation of the deviceunder typical conditions of traffic actuation.

In the embodiment of the invention shown at Fig. 6, the signal sequencedrum 103 is provided with six switching positions representing onecomplete cycle of operation. Since the apparatus is of the semi-actuatedtype, only a single position of the drum is a normal rest position. Thenormal rest position is position 1 in which it will be noted that thegreen signal is granted to the major lane A through the drum switch GA,and the red signal is displayed to the minor lane B through the drumswitch RB. It will be evident, of course, that since no detector isprovided in the major lane A, the drum will remain in position 1 and nochange will be eifected in the signal display so long as no tratiicapproaches on the minor lane B, regardless of the amount of traic o-nthe major lane A. In addition to the rest position 1 of the drum, thedrum is provided with a dwell position (position 4), in which the rightof way is accorded to lane B for a time determined by the density oftraffic o-n lane B, as will appear hereinafter.

Fig. 6 reverting- Transfer lane A lo lane B position 1 and that notraffic actuations have taken place for a considerable length of time sothat the entire apparatus is in a steady-state or standby condition. Inthis condition, the initial and extension interval timing tube for laneB, T-11, is conductive since the lane B recall switch R21 (closed forreverting operation) connects the cathode of T-11 to line L2, and thetiming capacitor C-11 is connected to a point 122 on potentiometer 123a,123b, 123C, which point is positive with respect to line lf2 when lineL-l is positive. The discharge tube T-31 is also conductive. This isbecause the cathode is connected directly to the supply line L-2 throughdrum co-ntact C24, and the grid is connected through the capacitor C-31to a point 110 on a potentiometer 109er, 109b, 109C, the point 108 beingpositive with respect to L-2 when L-1 is positive. The discharge tubeT-41 is maintained conductive for a similar reason, i. e., the cathodeis connected directly to L-2 through contacts 135, 135a on relay T11-21,while the grid is connected to a point 112 on a voltage divider 115e,115b, 115C. The discharge tube F1-51 is maintained non-conductive, bothbecause its cathode circuit is open at the drum contact C27, and becausea potentiometer 116:1, 116i), 116C is connected between the cathode oftube T-51 and the capacitor C-Sl through a resistor 117 and the contacts118, 118b of the relay TR-31 in a manner to maintain the grid negativewith respect to the cathode when the line L-l is positive.

With the discharge tubes in the foregoing condition, it will be observedthat the anode relays R-11, R-31 and R-41 are picked up, and the anoderelay R-51 is dropped out. In addition, it will be noted that the drumcontacts C-24, GA and RB are closed. The drum co-ntact C-24 connects thecathode of discharge tube T-31 to the line L-2. The drum contact GAenergizes the green light for lane A. The drum contact RB energizes thered light for lane B and also energizes the relay TR-31.

If now a vehicle actuation is received upon the minor and stopped laneB, the detector switch 101 is closed momentarily, thereby to complete anenergizing circuit for the detector timing relay DT-11 from the supplyline L-2 through a rectifier R', the switch 101, a capacitor 107, aresistor 119, and the actuating coil of the relay DT-11. The relay DT-11is energized only so long as current flows through this circuit tocharge the capacitor 107. A resistor 132 shunting capacitor 107 is solarge that insufficient current flows through it to hold the relay DT-llpicked up. While the relay DT-11 is thus picked up for an impulseinterval, it closes its contact 120, thereby to complete an energizingcircuit from the supply line L-Z for the actuating coil of the detectorrelay D-11. When the relay D-11 picks up, it opens its normally closedcontacts 121, 121a and closes its normally open contacts 121, 121b.Opening of the contacts 121, 121a interrupts the cathode circuit for thedischarge tube T-11 and renders this device non-conductive so that theplate relay R-11 drops out.

When the normally open contacts 121, 121k of the relay D-11 are closed,a charging circuit is completed for the capacitor C-11, which circuitmay be followed from a point 122 on a potentiometer 123g, 12317, 123C,through the capacitor C-11, the grid-to-cathode discharge space of thetube T-11, the contacts 121, 121]? of the relay D-11, and through thecontacts 124, 124m of the relay TR-li to the slider 140a of apotentiometer 140. Through this chargingcircuit, a single impulse orincrement of charge is placed upon the capacitor C-11 during theinterval while the relay D-11 is picked up. This charge times a singlevehicle initial interval for the lane B right of way, as willhereinafter appear.

Drop-out of the plate relay R-ll, as previously described, closes anormally closed contact 126 and also opens the normally open contact127. Opening Contact 127 has no effect at this time since, when closed,it was not included in any closed circuit. Closing of contact 126completes an energizing circuit for the motor 104 from the supply lineL-2 through the contact 130 of relay R-31, contacts 131, 131a of relay'FR-21 and the Contact 126. The motor 104 being energized, the drumadvances from position 1 to position 2.

In drum position 2, no change is effected in the lighting circuits, aswill be evident from the diagrammatic representation of the drum, butthe drum contacts C21, C23, C25 and C26 are closed, while the drumcontact C2.; is opened. Closure of drum contact C21 shunts the detectorswitch 101, thereby again to pick up relays DT--11 and D-11 for a secondimpulse interval and thus to add a second increment of initial intervalcharge to capacitor C-11. This automatic charging impulse insures asutilcient initial interval in the event that right of way is returnedto lane B by the memory circuit described hereinafter.

Closure of the drum contact C23 short circuits a resistor' 112 in thecharging circuit of the capacitor C-31. @pening of the drum contact C24interrupts the cathode circuit of the discharge tube T-31 thereby torender this device non-conductive and to render the charging circuit forC-31 operable. Closure of the drum contact C25 com'- pletes anenergizing circuit for the relay TR-21. This relay therefore picks upand remains energized through drum positions 2, 3 and 4 as will appearfrom the drum diagram. When the relay TR-21 picks up, it closes itscontacts 11141111, thereby to transfer the charging circuit for theextension limit timing capacitor C-31. This charging circuit may now befollowed from the point on the potentiometer 109a-109c through thecapacitor C31, the grid-to-cathode discharge space of the timing tubeT-31, the drum contact C23 and the contacts 111, 11111 on the relay'fR-21 to a slider 132 on a potentiometer 133 connected in parallelcircuit relation with the potentiometer section 109:1. Through thischarging circuit, the capacitor C-31 is charged to a voltagerepresenting an extension limit interval with the right of way on laneB. Drop-out of the plate relay R-31 and consequent opening of theContact 130 interrupt the drum motor ener- 2i gizing circuit so that themotor is braked to' a stop at position 2. The motor 104 is, however,again energized in drum position 2 by closure of drum contact C26 sothat the drum is advanced from position 2 to position 3.

When the drum 163 moves to position 3, the green light on lane A isdeenergized and the amber light on lane A is displayed through the drumcontact AA. In this position, phase A amber is timed and the drum isnext advanced in position by operation of the amber timing tube T-Sl.

In drum position 3, it may first be observed that drum contact C21 isopen, thereby to interrupt the energizing circuit for relay DT-11, whichrelay, however, was already dropped out by action of the blockingcapacitor 107. The relay D-11, being dropped out, completes the cathodecircuit of the discharge tube T-11. This discharge tube does not,however, conduct since the capacitor C-11 is now negatively charged andprovided with no discharge path. In this drum position 3 also, drumcontact C23 opens, thereby to unshunt the charging resistor 112. Thedrum contact C24 is reclosed thereby to reconnect the cathode of thedischarge tube T31 to the negative power supply line L-Z, and thuspermits the capacitor C-31 to begin discharging through resistor 129 and12951 in parallel, thereby to time the lane B extension limit interval.p

Amber timing-ln addition to the foregoing, drum contact C27 is closed indrum position 3, thereby to connect the cathode ofthe amber timing tubeT-Sl to the power supply line L-2. With the cathode thus connected,however, the tube T-51 does not immediately conduct because thecapacitor C-51 stood negatively charged by reason of its connection tothe potentiometer 116a-116c through the resistor 117 and the contact118, 118b of relay Til-31. Capacitor C-Sl now begins to dischargethrough the parallel-connected resistor 136 to time the amber displayinterval. When the capacitor C-51 is suiciently discharged so that thegrid-to-cathode voltage is substantially zero on positive half cycles ofsupply potential, the discharge tube T51 conducts and energizes itsplate relay ETSI. When the relay R-Sl picks up, it closes its normallyopen contact 137 thereby to complete an energizing circuit for the motor104 and advance the drum from position 3 to position 4.

ln drum position 4, the green light is displayed on lane B, the redlight interrupted on lane B, the amber light interrupted on lane A, andthe red light displayed on lane A, as will be evident from thediagrammatic illustration of drum switches GB, RB, AA and RA. 1n drumposition 4 also, the drum contact C27 is opened thereby to interrupt thecathode circuit of the timing tube T-51 and render this tubenon-conductive. Opening of the drum switch RB also deenergizes the relayTR-31 so that this relay drops out and closes its contacts 11.8, 118m.Transfer of the contact 118 by relay T11-31 substitutes for thepotentiometer section 11611 in the charging circuit of capacitor C-S, apotentiometer section 138 connected in parallel circuit relation withthe section 116a. Potentiometer 13S is adapted to determine a charge onthe capacitor C-il suitable for timing the amber interval on lane B, aswill hereinafter appear, while potentiometer 115g determines the lane Aamber interval.

Initial and extension timing-In drum position 4, drum contact C22 isclosed thereby to complete an energizing circuit for the transfer relayTRell. When the relay rlR-lli picks up, it closes its contact 139athereby to connect across the timing capacitor C-11 a discharge resistor139. The capacitor C-11 begins immediately to dissipate its negativecharge, thereby to time the initial right of way interval for lane B, aswill be evident from the foregoing description of Fig. 1. It will now beevident that any additional lane B detector actuations which took placein drum positions 1, 2 or 3, while the green or amber lights weredisplayed on lane A and the red light on lane B, will have repeatedlyenergized the detector relay D-11 for short impulse intervals deter@mined by the capacitor 107, thereby to store in the capacitor C-11additional increments of charge, the accumulated total of whichdetermines the initial interval for the right of way on lane B. It willhereinafter become evident that such initial interval charge for lane Balso accumulates in drum positions 5 and 6.

Pick-up relay TR-ll also transfers its contact 124 from 124g: to 124b,thereby to substitute in the charging circuit of the capacitor C11 apotentiometer section 123e for the potentiometer previously referred to.This provides a new charging circuit for capacitor C-11, adapted todetermine vehicle extension intervals whenever relay D-11 is picked upby cars approaching on lane B while it has the right of way. Thus, eachactuation of detector 101 when lane B has the right of way picks uprelays DT-11 and D-11 for a single impulse interval in the manneralready described. Relay D-11 when picked up interrupts the cathodecircuit of tube T-11 at contacts 121, 121a and completes a chargingcircuit for capacitor C-11 at contacts 121, 121b. The capacitor C-11 isthus charged to a voltage representing a single vehicle extensioninterval and retains the tube T-11 nonconductive for such interval. Thisaction is repeated by each vehicle approaching on lane B when it has theright of way. It will be understood that so long as tube T-11 isnon-conductive, the relay R11 is dropped out and precludes re-transferof the right oi way to lane A because contact 127 of relay R-11 is thusheld open to prevent short circuiting and rapid discharge of extensionlimit capacitor C-31 (which is presently discharging slowh ly throughresistors 129 and 129e to time the vehicle eX- tension limit interval).

It may now be noted, also, that whenever the detector 101 is actuated topick up the relays DT11 and D-11 for an impulse interval while lane Bhas the right of way, not only is an extension interval charge stored incapacitor C-11, but the tube T-41 is rendered non-conductive for a timedinterval to increase the extension limit time. This is because in drumposition 4 with lane B green the cathode of tube '1%41 is normallyconnected to L-2 through the contacts 135, 135b of relay TR*21 and thenormally closed contact 134 of detector relay D-11. When contact 134 ismomentarily opened by an actuation, the cathode circuit of tube T-41 isbroken and the tube rendered non-conductive. In this condition, thecapacitor C-41 is negatively charged by grid conduction on half cycleswhen L-1 is negative so that when contact 134 of relay D-11 reconnectsthe cathode of tube T-41 to line L-2, the tube r1141 remainsnon-conductive until the capacitor C-41 discharges through its shuntingresistor 140. During the interval while tube T-41 is thus shut 01T, theplate relay R-41 is dropped out and opens its contact 141 to unshunt theextension limit resistor 129, as described in connection with Fig. 1,thereby to increase the extension limit time.

The drum is moved off of position 4 when the timing tube T-11 againbecomes conductive as determined by the discharge interval of thecapacitor C-11. Now, therefore, when the initial interval charge and allextension interval charges on the capacitor C-11 are dissipated, thetube T-11 is again rendered conductive. When the discharge tube T-11becomes conductive, the plate relay R-11 is picked up, thereby to openthe contact 126 and close the contact 127. Opening ofthe contact 125 hasno effect, but closing of the contact 127 completes a short circuitaround the extension limit timing capacitor C-31, thereby immediately todischarge the capacitor C-31 and render the timing tube T-31 conductive.This short circuit may be followed from the grid of the tube r[-31,through the contacts 128, 128b of the transfer relay TR-21 and thecontact 127 of the relay R11 to the other side of the capacitor C-31.

Extension limit timing-It may here be noted that in the event thatvehicles continue to actuate the detector 101 while lane B has the rightof way and with sufficient frequency that vehicle extension intervalsare continuously demanded in Overlapping relation so that the timingtube T-11 never does become conductive, the extension limit capacitorC-31 eventually becomes discharged through the extension limit timingresistors 129, 129e. The tube T-31 is therefore rendered conductiveeither by reason of conduction of the tube T-11 after expiration of theinitial and all vehicle extension intervals (and consequent shortcircuiting of capacitor C-l), or by reason of the discharge of capacitorC-31 through the extension limit resistors 129, 129:1.

When the tube T-31 thus becomes conductive as described, its plate relayR-31 is picked up and closes its contact 130. With the transfer relayTil-21 now in its energized position, closure of the contact 130completes an energizing circuit for the drum advance motor 1&4, whichcircuit may be followed from the power supply line L-Z through theContact 135, the contacts 131, 13112 of the relay T11-21, and the drumadvance motor 104 to ground. The motor 104 thus being energized, thedrum 103 is advanced from position 4 to position 5.

Mininmm l1tervCll.-ln drum position 5, the drum contact C22 is opened,thereby to deenergize the transfer relay rI`R-11. When the relay Til-11drops out, it transfers its contact 124 to reconnect the chargingcircuit of the capacitor C-11 to the potentiometer 140, the initialinterval charging potentiometer. The drop-out of the relay TR-11 alsoopens the contacts 139g, thereby to interrupt the discharge circuit ofthe timing capacitor C-11. ln drum position 5, the drum contact C25 isalso opened, thereby to deenergize the transfer relay 'TR-21 and restoreit to its initial position, described in connection with drum positionl. As further appears from an examination of the drum diagram, movementof the drum to position effects no change in the lighting circuit butopens the drum contact C24 and closes the drum contact C23. Opening ofthe contact C24 interrupts the cathode circuit of the discharge tubeT-31, thereby to render this tube non-conductive, drop out the platerelay R-31, and open the motor energizing contact 139. Mornentaryclosure of drum contact C23 completes a charging circuit for capacitorC-31 from the potentiometer 109m. Through this circuit, capacitor C-31is charged to a voltage representing a minimum right of Way interval onlane A, in much the same manner as it is charged through drum contactC22 in drum position 2 to the maximum extension limit voltage. In drumposition 5, however, the energization of the motor 104 is maintainedthrough closure of the drum contact C26. The drum therefore advancesfrom position 5 to position 6.

Drum position 6 is the lane B amber interval, and the drum remains inthis position for a length of time de termined by the operation of theamber timing tube T-51. It will be noted that in drum position 6 the redlight remains on lane A but the green light is discontinued on lane Band the amber light on lane B substituted therefor. Opening of thc drumcontacts C in drum position 6 interrupts energization of the drumadvance motor 104, so that the motor is braked to a stop in position 6.

In drum position 6, the drum contact C23 is opened and the drum contactC24 closed, thereby to reconnect the cathode of the tube T-31 to thepower supply line L-Z and initiate discharge of the timing capacitorC-31 through the resistors 129 and 12961 in parallel. The dischargeinterval of the capacitor C-31 which is thus initiated represents theminimum right of way interval for lane A.

In drum position 6 also, the drum contact C27 is closed thereby tocomplete the cathode circuit for the amber timing tube T-S1. The ambertiming capacitor C-51 thus begins to discharge through the resistor 136from the charging voltage determined by the potentiometer 138, in thesame manner as it previously discharged in drum position 3 from thevoltage determined by the potentiometer 116e. The discharge tube T-Sllthus remains non-conductive in drum position 6 until the capacitor C-51is discharged. This discharge represents the amber timing interval forlane B. When the capacitor C-51 is discharged, the tube T-Sl becomesconductive, thereby to energize its plate relay R-51 and complete anenergizing circuit for the drum advance motor 16-4 through the contacts137. The motor 164 thus being energized, the drum advances from position6 to position 1. In drum position l, the drum contact C27 is opened,thereby to interrupt the cathode circuit for the tube T-51 and renderthat tube non-conclue tive. Drop-out of the associated plate relay R-Slinterrupts the motor energizing circuit and the motor 1M is braked to astop in drum position l.

Rest-In drum position l, the right of way is on lane A. Lane A is notprovided with a detector so that no initial interval or vehicleextension intervals are operative in connection with the lane A right ofWay interval. As previously noted, however, a minimum right of wayinterval for lane A is provided by charging the capacitor C-31 frompotentiometer 1t9a in drum position 5. Until this charge is dissipated,the discharge tube T-31 cannot become conductive and the plate relayR-31 remains dropped out. So long as the relay R-31 is dropped out, itscontact is open and no energizing circuit can be completed for the drumadvance motor 104, even though the tube T-11 is rendered non-conductiveby actuation of the lane B detector. in this connection, it will berecalled that transfer from drum position 1 to drum position 2 iseffected by completing a motor energizing circuit through. the Contact130 of relay 1?.-31, the contacts 131, 131a of relay TR-Zl, and thecontact 126 of relay R-11, all in series circuit relation. The Contact130 thus being held open for a lane A minimum interval, closure ofcontact 126 by vehicle actuations on lane B cannot immediately effecttransfer of the right of Way. Transfer is effected, however, as soon asthe lane A minimum interval expires so that tube 31 is ren deredconductive and the contact 13'() closed.

Minimum interval reduction It may now be noted, however, that during thepassage of the lane A right of way minimum interval, the minimuminterval may be shortened by actuations of the detector 101 on thestopped lane B. As previously noted, the lane A minimum interval isdetermined by discharge of the capacitor C-31 through resistors 129 and12911 in parallel. it will now be observed that with the transfer relayTR-21 in its dropped-out position, momentary pick-up of the detectorrelay D-11 for an impulse interval upon each actuation of the lane Bdetector completes, through a contact 142, a shunt circuit for thecapacitor C-31 through a resistor 143. This shunt circuit may befollowed from the grid of the tube T-31 through the contacts 128, 128gof the relay TF1-21, the contact 142 of the relay D-11, and the resistor143 to the other side of the capacitor C-31. Thus, whenever the lane Bdetector 161 is actuated during the lane A minimum right of Wayinterval, the resistor 143 is momentarily connected in parallel circuitrelation with the discharge resistors 129, 12.9(1, thereby momentarilyto accelerate the discharge of the capacitor C-31. 1n this manner,vehicles approaching the stopped lane B during the lane A minimum rightof way interval are effective to decrease this minimum interval inincrements.

It will now be evident to those skilled in the art that if the lane Aright of way minimum interval expires without any actuation of thedetector 1111 on lane B, the apparatus is again in the standby conditionwith which the description of the operation was initiated.

25 Memory recall Let it now be supposed, however, that the retransfer ofthe right of way to lane was elfected by operation of the extensionlimit, rather than by expiration of all vehicle extension intervals onlane B, so that a vehicle is still on lane B between the detector andthe light. In this case, the timing capacitor C-11 would have been onlyincompletely discharged at the time that the drum was moved off position4, and its discharge circuit broken. The tube T-Il thus remainsnon-conductive throughout drum positions S and 6, and is stillnon-conductive in drum position l when the lane A minimum intervalexpires. The tube T-ll thus being non-conductive, its plate relay R-l isdropped out and the plate relay contacts 126 close. Therefore, when thelane A minimum interval expires and the tube T-Sl is renderedconductive, pick-up of the associated plate relay R-31 completes, byclosure of the contact 30, a drum motor energizing circuit in the samemanner as that initially described when drum position 1 was firstconsidered. It will now be evident that in this memory type recalloperation, the small negative charge still remaining upon the timingcapacitor C-lll may not be suiicient to permit the vehicle stored onlane B to be cleared. It is for this purpose that the capacitor C-11 isrecharged in drum position 2 through closure of the drum contact C21 aspreviously described.

Fig. 6.-Cyclc Finally, it will now be observed that normally cyclicoperation of the controller shown in Fig. 6 may be effected by openingthe recall switch R21. When the switch R21 is opened, the cathodecircuit of the tube T-ll is interrupted so that the plate relay R-lremains dropped out at all times, thereby to leave the contacts 126continuously closed. Continous closure of the contact 126 acts as arecall of the right of way to lane B so that the apparatus continuallygoes through a cyclic alternation of the right of way, even in theabsence of vehicle actuation. It will, of course, be appreciated thatduring this cyclic operation, actuation of the lane B detector 101,while lane A has the right of way, reduces the lane A minimum interval,in the same manner previously described. Similarly, actuations of thelane B detector i when lane B has the right of way introduce vehicleextension intervals and increase the lane B extension limit time in thesame manner previously described.

Operation at intersection of more than two trac lanes it will now beevident to those skilled in the art that my new and improved controlleris equally applicable to intersections of three or more traic lanes, orstreets. For example, in the full actuated controller of Fig. l, it isonly necessary to provide, for a three-street controller, a twenty-fourposition drum controller, another initial and extension interval timerconnected in parallel with the timers which include tubes T-l and T-2,and transfer relays having, in proper circumstances, three rather thantwo selector positions. The timing tubes T-3, T-4 and T-S, being commonto all lanes, may readily be transferred between three streets in likemanner as they are shown transferred between two streets. It is, ofcourse, additionally necessary to provide a third pair or" detectors anda third detector relay and detector timing relay, these also beingconnected in parallel relationship with the like components illustrated.Thus, by simple paralleling of additional similar components, itisclearly possible to utilize my controller for intersections of two,three or more intersecting traiiic lanes. It will be similarly evidentthat the semi-actuated controller of Fig. 6 may be expanded in likemanner to control intersections of more than two streets, detectors andinitial interval timers being provided in such case for all except theone main street or lane.

While I have described only certain preferred embodiments of myinvention by way of illustration, many modilications will occur to thoseskilled in the art, and I therefore wish to have it unlerstood that Iintend in the appended claims to cover all such modifications as fallwithin the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In a vehicle actuated traic signal control apparatus including asignal device providing stop and go indications for each of a pluralityof intersecting trac lanes, signal switching means connected to accordsaid go indication successively to said lanes, a vehicle actuated deviceon at least one of said lanes, means controlled by said vehicle actuateddevice when said lane has said stop indication for actuating said signalswitching means to accord said go indication to said lane, timing meanscontrolled by said vehicle actuated device when said lane previously hadsaid stop indication for predetermining au initial go indicationinterval on said one lane, means responsive to each actuation of saidvehicle actuated device when said one lane has said go indication forcontrolling said timing means to extend said go indication beyond saidinitial interval and until a predetermined time after said actuation,and separate timing means controlled by said switching means andoperable after a limiting interval to render said rst timing meansineffective to extend said go indication and to operate said signalswitching means to remove said go indication from said one lane.

2. In a vehicle actuated traiiic signal control apparatus including asignal device providing stop and go indications for each of a pluralityof intersecting traffic lanes, signal switching means connected toaccord said go indication successively to said lanes, means actuated byeach vehicle approaching said device on a lane having a go indication toextend said go indication, timing means operable after a limitinginterval to render said extending means ineffective, and means actuatedby each vehicle approaching said device on a lane having a go indicationto increase said limiting interval.

3. In a vehicle actuated trali'ic signal control apparatus including asignal device providing stop and go indications for each of a pluralityof intersecting traffic lanes, signal switching means connected toaccord said go indication successively to said lanes, vehicle actuateddevices on at least two of said lanes, means controlled by a vehicleactuated device on a lane having a go indication to extend said goindication, separate timing means operable after a limiting interval torender said extending means ineffective, and means concurrentlycontrolled by all said vehicle actuated devices for incrementallycontrolling the length of said limiting interval.

4. In a vehicle actuated traiic signal control apparatus including asignal device providing stop and go indications for each of a pluralityof intersecting traitic lanes, signal switching means connected toaccord said go indication successively to said lanes, means actuated bya vehicle approaching said device on a lane having a go indication toextend said go indication, timing means operable after a limitinginterval to render said extending means ineliective, and means actuatedby each vehicle approaching said device on a lane having a stopindication to reduce said limiting interval.

5. In a vehicle actuated tra'ic signal control apparatus including asignal device providing stop and go indications for each of a pluralityof intersecting traiiic lanes, signal switching means connected toaccord said go indication successively to said lanes, means actuated byeach vehicle approaching said device on a lane having said go indicationto extend said go indication, timing means operable after a limitinginterval to render said extending means ineffective, means actuated byeach vehicle approaching said device on a lane having a go indication toincrease said limiting interval, and meansactuated by each vehicleapproaching said device on a lane having a stop indication to reduce thesaid limiting in- 27 terval then running on the lane having said goindication.

6. In a vehicle actuated trac signal control apparatus including asignal device providing stop and go indications for each of a pluralityof intersecting traffic lanes, signal switching means connected toaccord said go indication successively to said lanes, a vehicle actuateddevice on at least one of said lanes, an electron discharge devicehaving an anode, a cathode and a control electrode, means responsive toconduction of said discharge device for actuating said signal switchingmeans to transfer said go indication from one lane to another, timingmeans including a capacitor connected to said control electrode formaintaining said discharge device non-conductive when said capacitor ischarged, means controlled by said vehicle actuated device when Said onelane has said go indication for charging said capacitor to apredetermined voltage upon each vehicle actuation, and second timingmeans for rendering said first timing means ineffective to extend saidgo indication and for actuating said signal switching means to removesaid go indication from said one lane after a limiting right of wayinterval.

7. In a vehicle actuated traffic signal control apparatus including asignal device providing stop and go indications for each of a pluralityof intersecting traffic lanes, signal switching means connected toaccord said go indication successively to said lanes, a vehicle actuateddevice on at least one of said lanes, an electron discharge devicehaving an anode, a cathode and a control electrode, means responsive toconduction of said discharge device for actuating said signal switchingmeans to transfer said go indication from one lane to another, timingmeans including a capacitor connected to said control electrode formaintaining said discharge device non-conductive when said capacitor ischarged, means controlled by said vehicle actuated device when said onelane has said stop indication for incrementally charging said capacitorto a voltage proportional to the number of vehicles actuating saidvehicle actuated device, means controlled by said vehicle actuateddevice when said one lane has said go indication for charging saidcapacitor to a predetermined voltage upon each such vehicle actuation,and second timing means for rendering said first timing meansineffective to extend said go indication and for actuating said signalswitching means to remove said go indication from said one lane after alimiting right of way interval.

8. In a vehicle actuated traffic signal control apparatus including asignal device providing stop and go indications for each of a pluralityof intersecting traffic lanes, signal switching means connected toaccord said go indication successively to said lanes, a vehicle actuateddevice on at least one of said lanes, means controlled by said vehicleactuated device when said one lane has said stop indication foractuating said signal switching means to accord said go indication tosaid lane, second switching means for actuating said signal switchingmeans to remove said go indication from said one lane, first timeelement means for disabling said second switching means, meanscontrolled by said vehicle actuated device for controlling said firsttime element means to retain said go indication on said one lane for atleast an initial interval after accord of said go indication, meansresponsive to each actuation of said vehicle actuated device when saidone lane has said go indication for controlling said first time elementmeans to extend said go indication for a predetermined intervalfollowing each said actuation, and second time element means forrendering said first timing means ineffective to extend said goindications and for energizing said second switching means to removesaid go indication from said one lane after an extension limitinginterval.

9. ln a vehicle actuated traffic signal control apparatus including asignal device providing stop and go indications for each of a pluralityof intersecting trac lanes, signal switching means connected to accordsaid go indication successively to said lanes, means actuated by avehicle approaching said device on at least one of said lanes when saidlane has said stop indication for actuating said signal switching meansto accord said go indication to said one lane, first timing meanscontrolled by said signal switching means to retain said go indicationon said one lane for at least an initial interval, means responsive toeach additional actuation of said vehicle actuated means while said onelane has said go indication for controlling said first timing means toextend said go indication, second timing means controlled by said signalswitching means for rendering said first timing means ineffective toextend said go indication and for operating said signal switching meansto remove said go indication from said one lane after an extensionlimiting interval, and means responsive to each said additionalactuation for incrementally increasing said extension limiting interval.

10. in a vehicle actuated traffic signal control apparatus including asignal device providing stop and go indications for each of a pluralityof intersecting traffic lanes, signal switching means connected toaccord said go indication successively to said lines, a vehicle actuateddevice on at least one of said lanes, means controlled by said vehicleactuated device when said one lane has said stop indication foractuating said signal switching means to accord said go indication tosaid one lane, second switching means for actuating said signalswitching means to remove said go indication from said one lane, firsttiming means for disabling said second switching means, means controlledby said vehicle actuated device when said one lane has said stopindication for controlling said first timing means to retain said goindication upon said one lane for at least an initial interval afteraccord to said one lane, means responsive to each additional actuationof said vehicle actuated device while said one lane has said goindication for controlling said first timing means to extend said goindication for a predetermined interval after each such actuation,second timing means controlled by said signal switching means forrendering said first timing means ineffective to extend said goindication and for rendering said second switching means effective toremove said go indication from said one lane after an extension limitinginterval, and means responsive to each said additional actuation forincrementally increasing said limiting interval.

1l. In a vehicle actuated trafic signal control apparatus including asignal device providing stop and go indications for each of a pluralityof intersecting traflic lanes, signal switching means connected toaccord said go indication successively to said lanes, a vehicle actuateddevice on at least one of said lanes, means controlled by said vehicleactuated device when said one lane has said stop indication foractuating said signal switching means to accord said go indication tosaid one lane, second switching means for actuating said signalswitching means to remove said go indication from said one lane, firsttime element means for disabling said second switching means, meansresponsive to actuations of said vehicle actuated device when said onelane has said stop indication for controlling said first time elementmeans to maintain said go indication on said one lane for at least aninitial interval after accord thereto, means responsive to eachactuation of said vehicle actuated device while said one lane has saidgo indication for controlling said first time element means to extendsaid go indication for a predetermined interval following each suchactuation, second time element means controlled by said signal switchingmeans for rendering said second switching means effective to remove saidgo indication after a predetermined extension limiting interval, andmeans responsive to each said last-named actuation of said vehicleactuated device for incrementally increasing said extension limitinginterval.

12. In a vehicle actuated traffic signal control apparatus including asignal device providing stop and go indications for each of a pluralityof intersecting traiiic lanes, signal switching means connected toaccord said go indication successively to said lanes, a vehicle actuateddevice on each said lane, second switching means controlled by thevehicle actuated device on a stopped lane for operating said signalswitching means to accord said go indication to that lane, first timingmeans controlled by the vehicle actuated device on each lane prior toaccord of said go indication to that lane to retain said go indicationon that lane for at least an initial interval after accord of said goindication, second timing means controlled by the vehicle actuateddevice on a moving lane for rendering said second switching meansineffective to operate said signal switching means for an extensioninterval after each moving lane actuation, third timing means controlledby said signal switching means for rendering said second timing meansineffective to extend said go indication after an extension limitinginterval, and means controlled by said vehicle actuated device on amoving lane to incrementally increase said extension limiting interval.l

13. In a vehicle actuated traffic signal control apparatus including asignal device providing stop and go indications for each of a pluralityof intersecting traffic lanes, signal switching means connected toaccord said go indication successively to said lanes, a vehicle actuateddevice on each said lane, second switching means controlled by thevehicle actuated device on each lane when stopped for actuating saidsignal switching means to accord said go indication to that lane, anelectron discharge device controlled by the vehicle actuated device ineach lane and each including an anode, a cathode and a controlelectrode, means controlled by said signal switching means forconnecting the discharge device associated with a moving lane whenconductive to render said second switching means effective to remove thego indication from that lane, means responsive to the vehicle actuateddevice on a moving lane for controlling the control electrode potentialof the associated discharge device to render said discharge devicenon-conductive for a predetermined interval following each such vehicleactuation, timing means for rendering said second switching meanseffective to remove said go indication from a moving lane after anextension limiting interval independently of conduction of theassociated discharge device, and means responsive to each actuation ofsaid vehicle actuated device on a moving lane for controlling saidtiming means to incrementally increase said extension limiting interval.

14. In a vehicle actuated trafiic signal control apparatus including asignal device providing stop and go indications for each of a pluralityof intersecting traffic lanes, electroresponsive signal switching meansconnected to accord said go indication successively to said lanes, anelectron discharge device having an anode, a cathode and a controlelectrode, means operable upon conduction of said discharge device toactuate said signal switching means to transfer said go indication froma first to a second lane, a capacitor connected when charged to maintainsaid control electrode negative with respect to said cathode thereby torender said discharge device nonconductive, a resistor connected acrosssaidr capacitor to control the discharge thereofV thereby to time aninterval, a second resistor adapted to be connected in shunt circuitrelation with said first resistor, and means controlled by vehiclesapproaching said signal device on at least one of said lanes forcontrolling said shunt circuit connection thereby to control the rate ofdischarge of said capacitor and the'length of said interval.

l5. In a vehicle actuated trafic signal control apparatus including asignal device providing stop and go indications for each ofv a pluralityof intersecting tratic lanes, electroresponsive signal switching meansconnected to accord said go indication successively to said lanes, anelectron discharge, device having an anode, a cathode and a controlelectrode, means operable upon conduction of said discharge device toactuate said signal switching means to transfer said go indication froma first to a second lane, a capacitor connected when charged to maintainsaid control electrode negative with respect to said cathode thereby torender said discharge device nonconductive, a resistor connected acrosssaid capacitor to control the discharge thereof thereby to time aninterval, and means controlled by vehicles approaching said signaldevice on at least one of said lanes for momentarily connecting in shuntcircuit relation with said resistor a second resistor therebyincrementally to reduce the length of said interval.

16. In a vehicle actuated traic signal control apparatus including asignal device providing stop and go indications for each of a pluralityof Aintersecting traflic lanes, electroresponsive signal switching meansconnected to accord said go indication successively to said lanes, anelectron discharge device having an anode, a cathode and a controlelectrode, means operable upon conduction of said discharge device toactuate said signal switching means to transfer said go indication froma first to a second lane, a capacitor connected when charged to maintainsaid control electrodenegative with respect to said cathode thereby torender said discharge device nonconductive, a resistor connected acrosssaid capacitor to control the discharge thereof thereby to time aninterval, and means controlled by vehicles approaching said signaldevice on at least one of said lanes for momentarily disconnecting saidresistor from said capacitor thereby to reduce the rate of discharge ofsaid capacitor and incrementally increase the length of said interval.

17. In a vehicle actuated traffic signal control apparatus including asignal device providing stop and go indications for each of a pluralityof intersecting traiiic lanes, electroresponsive signal switching meansconnected to accord said go indication successively to said lanes, anelectron discharge device having an anode, a cathode and a controlelectrode, means operable upon conduction of said discharge device toactuate said signal switching means to transfer said go indication froma first to a second lane, a capacitor connected when charged to.maintain said control electrode negative with respect to said cathodethereby to render said discharge device non-conductive, a resistorconnected across said capacitor to control the discharge thereof therebyto time an interval, a second resistor normally connected in shuntcircuit relation with said first resistor, and means recurrentlyactuated by each vehicle approaching said signal device on a moving lanefor momentarily disconnecting said second resistor thereby to reduce therate of discharge of said capacitor and incrementally increase thelength of said interval. Y

18. In a vehicle actuated trafiic signal control apparatus including asignal device providing stop and go indications for each of a pluralityof intersecting traffic lanes, electroresponsive signal switching meansconnected to accord said go indication successively to said lanes, anelectron discharge device having an anode, a cathode and a controlelectrode, means operable upon conduction of said discharge device toactuate said signal switching means to transfer said go indication froma first to a second lane, a capacitor connected when charged to maintainsaidcontrol electrode negative with respect to said cathode thereby torender said discharge device non-conductive, a resistor connected acrosssaid capacitor to controlthe discharge thereof thereby to time aninterval, a second resistor, and means recurrently actuated by vehiclesapproaching said signal device on a lane having said stop indication formomentarily connecting said second resistor in parallel circuit relationwith said capacitor thereby to increase the rate of discharge of saidcapacitor and incrementally'to decrease the length of said interval.

19. In a vehicle actuated traiic signalv control apparatus including asignal device providing stop and go indications for each of a pluralityof intersecting traffic lanes, electro-responsive signal switching meansconnected to accord said go indication successively to said lanes, anelectron discharge device having an anode, a cathode and a controlelectrode, means operable upon conduction of said discharge device toactuate said signal switching means to transfer said go indication froma rst to a second lane, a capacitor connected when charged to maintainsaid control electrode negative with respect to said cathode thereby torender said discharge device nonconductive, a resistor connected acrosssaid capacitor to control the discharge thereof thereby to time aninterval, a second resistor adapted to be connected in shunt circuitrelation with said first resistor, a third resistor normally connectedin shunt circuit relation with said first resistor, means recurrentlyactuated by vehicles approaching said signal device on a lane havingsaid stop indication for momentarily connecting said second resistor inshunt with said first resistor thereby to increase the rate of dischargeof said capacitor and incrementally to reduce said interval, and meansrecurrently actuated by vehicles approaching said signal device on alane having said go indication for momentarily disconnecting said thirdresistor from said capacitor thereby to decrease the rate of dischargeof said capacitor and incrementally to increase said interval.

20. In a vehicle actuated traic signal control apparatus including asignal device providing stop and go indications for each of a pluralityof intersecting trac lanes, signal switching means connected to accordsaid go indication successively to said lanes, a vehicle actuated deviceon each of said lanes, means controlled by the vehicle actuated deviceon a stopped lane for operating said signal switching means to accordsaid go indication to said stopped lane, means controlled by the vehicleactuated device on a moving lane for rendering each vehicle actuateddevice on a stopped lane ineffective to operate said signal switchingmeans for an extension interval after each moving lane actuation, timingmeans controlled by said signal switching means for rendering said meansresponsive to actuations on a moving lane ineffective after an extensionlimiting interval, and means responsive to each actuation of the vehicleactuated device on a stopped lane for controlling said timing means toincrementally decrease said extension limiting interval.

2l. In a vehicle actuated trac signal control apparatus including asignal device providing stop and go indications for each of a pluralityof intersecting traic lanes, signal switching means connected to accordsaid go indication successively to said lanes, a vehicle actuated deviceon each of sai-d lanes, second switching means controlled by the vehicleactuated device on a stopped lane for actuating said signal switchingmeans to accord said go indication to that lane, rst timing means fordisabling said second switching means, means actuated by the vehicleactuated device ou a stopped lane for controlling said first timingmeans to maintain said second switching means disabled for at least aninitial interval after said go indication is accorded to said lane,means actuated by the vehicle actuated device on a moving lane forcontrolling said rst timing means to maintain said second switchingmeans disabled for a predetermined extension interval following eachmoving lane actuation, second timing means controlled by said signalswitching means for operating said second switching means independentlyof said rst timing means after an extension limiting interval, and meansactuated by the vehicle actuated device on a stoppedv lane forrecurrently and incrementally decreasing said extension limitinginterval.

22. In a vehicle actuated trac signal control apparatus including asignal device providing stop and go indications for each of a pluralityof intersecting traffic lanes, sinal switching means connected to accord4said go indication successively to said lanes, vehicle actuated deviceson all except one of said lanes, means controlled by a vehicle actuateddevice on a stopped lane for actuating said signal switching means toaccord said go indication to said stopped lane, means controlled by saidsignal switching means to thereafter return said go indication to saidone lane, timing means controlled by said signal switching means andeffective upon such return of said go indication to said one lane torender said vehicle actuated devices ineffective to actuate said signalswitching means for at least a minimum right of way interval, andadditional means controlled by said vehicle actuated devices during saidminimum interval to reduce said interval in increments in response toeach vehicle approaching the signal device on a stopped lane.

23. in a vehicle actuated tratlic signal control apparatus including asignal device providing stop and go indications for each of a pluralityof intersecting trac lanes, signal switching means connected to accordsaid go indication successively to said lanes, vehicle actuated deviceson all except one of said lanes, means controlled by the vehicleactuated device on a stopped lane for actuating said signal switchingmeans to accord said go indication to said stopped lane, meansresponsive to each actuation of the vehicle actuated device on a movinglane for extending the go indication then accorded to that lane, meanscontrolled by said signal switching means for returning said goindication to said one lane, timing means controlled by said signalswitching means and effective upon such return of said go indication tosaid one lane to render said vehicle actuated devices ineltective toactuate said signal switching means for at least a minimum right of wayinterval, and additional means controlled by said vehicle actuateddevices during said minimum interval to reduce sai-d minimum interval inincrements in response to each vehicle approaching the signal device ona stopped lane.

24. In a vehicle actuated traic signal control apparatus including asignal device providing stop and go indications for each of a pluralityof intersecting traic lanes, signal switching means connected to accordsaid go indication successively to said lanes, vehicle actuated deviceson all except one of said lanes, means controlled by a vehicle actuateddevice on a stopped lane for actuating said signal switching means toaccord said go indication to said stopped lane, means responsive to eachactuation of a vehicle actuated device on a moving lane to extend for apredetermined interval beyond such actuation the go indication thenaccorded to that lane, timing means operable upon accord of said goindication to a lane to disable said extending means after a limitingtime interval, means responsive to each actuation of the vehicleactuated device on a moving lane during said limiting time intelval forincrementally increasing said limiting time interval, means controlledby said signal switching means to return said go indication to said onelane, second timing means controlled by said signal switching means andeffective upon such return of said go indication to said one lane torender said vehicle actuated devices ineffective to actuate said signalswitching means for at least a minimum right of way interval, andadditional means controlled by said vehicle actuated devices during saidminimum ,interval to reduce sai-d interval by increments in response toeach vehicle approaching the signal device ona stopped lane.

25. In a vehicle actuated traffic signal control apparatus including asignal device providing stop and go indications for each of ay pluralityof intersecting traic lanes, signal switching means connected to accordsaid go indication successively to said lanes, vehicle actuated deviceson all except one of said lanes, electro-responsive means for actuatingsaid signal switching means, an electron discharge device connected whenconductive to energize said electro-responsive means, means controlledby a vehicle actuated device on a stopped lane for rendering attivistasaid discharge device conductive thereby to actuate saidl signalswitching means to accord said go indication to said stopped lane, meanscontrolled by said signal switching means for rendering said dischargedevice conductive thereby to actuate said signal s witching means toreturn said go indication to said one lane, time element meansresponsive to each actuation of a vehicle actuated device on a movinglane for maintaining said discharge device non-conductive for apredetermined time interval beyond such actuation thereby to extend thego indication then accorded to that lane, lirst timing means including acapacitor connected to control said discharge device and operable aftera limiting time interval following accord of said go indication to amoving lane to render said discharge device conductive independently ofsaid time element means thereby to actuate said signal switching means,means responsive to each actuation of a vehicle actuated device on amoving lane during said limiting time interval for controlling saidcapacitor to incrementally increase said limiting time interval, secondtiming means controlled by said signal switching means and effectiveupon such return of said go indication to said one lane to maintain saiddischarge device non-conductive for at least a minimum right of wayinterval, and additional means controlled by said vehicle actuateddevices during said minimum interval to control said capacitor to reducesaid minimum interval in increments in response to each vehicleapproaching said signal device on a stopped lane.

26. in a vehicle actuated traic signal control apparatus including asignal device providing st op and go'indications for each of apluralityof intersecting trafic lanes, signal switching means connectedto accord said go indication successively to said lanes, a vehicleactuated device on each of said lanes, second switching means controlledby the vehicle actuated device on a stopped lane for actuating saidsignal switching means to accord said go indication to that lane, firsttiming means controlled by the vehicle actuated device on a lane priorto accord of the go indication to that lane for retaining said goindication on that lane for at least an initial interval after accord ofsaid go indication, second timing means controlled by the vehicleactuated device on a moving lane for rendering said second switchingmeans inelective to operate said signal switching means for an extensioninterval after each moving lane actuation, third timing means controlledby said signal switching means for rendering said second timing meansinelective to retain said go indication on a moving lane after anextension limiting interval, third switching means responsive to thevehicle actuated device on a moving lane for controlling said thirdtiming means to incrementally increase said extension limiting interval,and fourth switching means responsive to the vehicle actuated device ona stopped lane for controlling said third timing means to incrementallydecrease said extension limiting interval.

27. In a vehicle actuated traic signal control apparatus including asignal device providing stop and go indications for each of a pluralityof intersecting trac lanes, signal switching means connected to accordsaid go indication successively to said lanes, a vehicle actuated deviceon each of said lanes, second switching means controlled by the vehicleactuated device on a stopped lane for operating said signal switchingmeans to accord said go indication to that lane, first time elementmeans controlled by the vehicle actuated device on a lane prior toaccord of said go indication to that lane for retaining said go indica.-tion on that lane for at least an initial interval after accord of saidgo indication, second time element means controlled by the vehicleactuated device on a moving lane for rendering said second switchingmeans ineiiective to operate said signal switching means for anextension interval after each moving lane actuation, an electrondischarge device connected when conductive to actuate Vsaid signalswitching means independently of said second time element means, acapacitor connected to control conduction of said discharge device, apair of resistors connected in shunt circuit relation with vsaidcapacitor to time a normall extension limiting interval after accord ofsaid go indication to a lane, third switching means responsive to thevehicle actuated device on a moving lanev for momentarily disconnectingone of said resistors from said capacitor thereby incrementally toincrease said extension limiting interval, and means responsive to avehicle actu ated device on a'st'opped lane for momentarily connectingin shunt circuit relation with said capacitor a third resistor therebyincrementally to decrease said extension limiting interval. l

28. In a vehicle actuated tratic signal control apparatus including asignal device providing stop and go indications for each of aplurality'of intersecting traiic lanes,` signal switching meansconnected to accord said go indication successively to said lanes, avehicle actuated device on each of said lanes, second switching meanscontrolled by the vehicle actuated device on a stopped lane foractuating said signal switching means to accord said go indication tothat lane, irst timingl means controlled by the vehicle actuated deviceon a lane prior to accord of said go indication to said lanefor'retaining said go indication on said lane for at least an initialinterval after accord of said go indication, second timing meanscontrolled by the vehicle actuated'device on a moving lane for renderingsaid second switching means inetective to actuate said signal switchingmeans for extension interval after each`moving lane actuation, thirdtiming means controlled by said signal switching means for renderingsaid second timing means ineffective to extend said go indication afteran extension limiting interval, third switching means momentarilyresponsive to operation of the vehicle actuated device on a moving lanefor controlling said third timing means to incrementally increase saidextension limiting interval, fourth switching means momentarilyresponsive to the operation of the vehicle actuated device on a stoppedlane 'for controlling said third timing means to incrementally reducesaid extension limiting interval, and means forming part of said thirdtiming means for predetermining an ultimate extension limiting intervaloperable despite' substantially cQntinuOuS .Operation of said thirdswitching means.

29. In a vehicle actuated tratic signal control apparatus including asignal device providing stop and go indications for each of a pluralityof intersecting traic lanes, signal switching means connected to accordsaid go indication successively to said lanes, a vehicle actuated deviceon at least one of said lanes, second switching means controlled by saidvehicle actuated device when said one lane has said stop indication foractuating said signal switching means to accord said go indication tosaid 'one lane, tirst timing means controlled by said vehicle actuateddevice on said one lane when said one lane has said stop indicationforlpredetermining a subsequent initial right of way interval for saidone lane proportional to the number of vehicle actuations on said lanewhen stopped, second timing means controlled by said vehicle actuateddevice on said lane when Vsaid one lane has said go indication forrendering said rst switching means ineffective to remove said goindication for at least a predetermined extension interval after eachmoving lane vehicle actuation, third timing means for actuating saidsignaly switching means to remove said go indication from said one laneindependently of said second timing means after an extension limitinterval, and second switching means controlled by said vehicle actuatedmeans on said one lane when said one ,lane has said stop indication forinitiating timing operation of said third timing means- 3(). In avehicle actuated traflic signal control apparatus including a signaldevice providing stop and go indications for each af a plurality ofintsrsetins fra lanes,

